This function takes around 1.2 seconds to execute. I am unable to understand why? Is it because of the inner joins? If yes, then how can i improve the execution speed? I am using Microsoft Enterprise Library.
Public Shared Function GetDataByInterests(ByVal accountId As Integer) As Object
Dim details As New List(Of GetIdBasedOnInterest)()
Dim getIDs As New GetIdBasedOnInterest
Dim interests As String = ""
Dim db As SqlDatabase = Connection.Connection
Using cmdGeneric As DbCommand = db.GetSqlStringCommand("SELECT Interests.InterestName FROM UserInterests INNER JOIN Interests ON UserInterests.InterestID = Interests.InterestID WHERE UserInterests.AccountID=#AccountID")
db.AddInParameter(cmdGeneric, "AccountID", SqlDbType.Int, accountId)
Dim dsInterests As DataSet = db.ExecuteDataSet(cmdGeneric)
For i = 0 To dsInterests.Tables(0).Rows.Count - 1
If i = dsInterests.Tables(0).Rows.Count - 1 Then
interests = interests & dsInterests.Tables(0).Rows(i).Item(0).ToString
Else
interests = interests & dsInterests.Tables(0).Rows(i).Item(0).ToString & ","
End If
Next
End Using
getIDs.InterestName = interests
details.Add(getIDs)
Return details
End Function
Without knowing anything of the underlying tables and their indexes (and this is a check you should do immediately) there is an obvious problem in your loop.
You cancatenate strings, this, potentially could pose a strong pressure on the memory used by your program.
A string concatenation results in a new string allocated on the memory and thus, if your table contains many rows, the effect could be noticeable.
You could try to use a StringBuilder
Dim interests As new StringBuilder(1024) ' suppose an internal buffer of 1K'
...
If i = dsInterests.Tables(0).Rows.Count - 1 Then
interests.Append(dsInterests.Tables(0).Rows(i).Item(0).ToString)
Else
interests.Append(dsInterests.Tables(0).Rows(i).Item(0).ToString & ",")
End If
....
getIDs.InterestName = interests.ToString
Of course this optimization could be absolutely not important if your tables (UserInterests and Interests) are not correctly indexed on the fields InterestID and AccountID
EDIT: Another micro-optimization is to remove the internal IF test and truncate the resulting output only after the loop ends
For ....
interests.Append(dsInterests.Tables(0).Rows(i).Item(0).ToString & ",")
Next
if(interest.Length > 0) interest.Length -= 1;
EDIT As for your request, this is an example to create an unique index. The syntax could be more complex and varying depending on the Sql Server version, but basically you do this in Sql Management Studio
CREATE UNIQUE INDEX <indexname> ON <tablename>
(
<columntobeindexed>
)
Check the CREATE INDEX statement examples on MSDN
1) Time your query in SQL Server Management studio. It will be much easier to tune it there in isolation from your VB code. Also you can run the display the query plan, and it ight even suggest new indexes.
2) Check you have the relevent primary keys and indexes defined.
3) Pull common expressions out of your for loop, to avoid recomputing the same thing over and over:
4) Like Steve says, use a StringBuilder
Combining those points:
Dim theTable as ...
Dim rowCount as Integer
Dim interests As new StringBuilder(1024)
Set theTable = dsInterests.Tables(0)
rowCount = theTable.Rows.Count
For i = 0 To rowCount - 1
interests.Append(theTable.Rows(i).Item(0).ToString)
If i <> rowCount - 1 Then
interests.Append(",")
End If
Next
Related
I have a query called qryAlloc_Source that has two paramaters under one criteria:
>=[forms]![frmReportingMain]![txtAllocStart] And <=[forms]![frmReportingMain]![txtAllocEnd])
A have a separate query that ultimately references qryAlloc_Source (there are a couple queries in between), and that query runs fine when I double click it in the UI, but if I try to open it in VBA, I get an error. My code is:
Dim rst As Recordset
Set rst = CurrentDb.OpenRecordset("qryAlloc_Debits")
I am getting run-time error 3061, Too few parameters. Expected 2. I've read that I may need to build out the SQL in VBA using the form parameters, but it would be pretty complex SQL given that there are a few queries in the chain.
Any suggestions as to a workaround? I considered using VBA to create a table from the query and then just referencing that table--I hate to make extra steps though.
The reason you get the error when you just try to open the recordset is that your form is not open and when you try to access [forms]![frmReportingMain] it's null then you try to get a property on that null reference and things blow up. The OpenRecordset function has no way of poping up a dialog box to prompt for user inputs like the UI does if it gets this error.
You can change your query to use parameters that are not bound to a form
yourTableAllocStart >= pAllocStart
and yourTableAllocEnd <= pAllocEnd
Then you can use this function to get the recordset of that query.
Function GetQryAllocDebits(pAllocStart As String, pAllocEnd As String) As DAO.Recordset
Dim db As DAO.Database
Dim qdef As DAO.QueryDef
Set db = CurrentDb
Set qdef = db.QueryDefs("qryAlloc_Debits")
qdef.Parameters.Refresh
qdef.Parameters("pAllocStart").Value = pAllocStart
qdef.Parameters("pAllocEnd").Value = pAllocEnd
Set GetQryAllocDebits = qdef.OpenRecordset
End Function
The disadvantage to this is that when you call this now on a form that is bound to it it doesn't dynamically 'fill in the blanks' for you.
In that case you can bind forms qryAlloc_debts and have no where clause on the saved query, then use the forms Filter to make your where clause. In that instance you can use your where clause exactly how you have it written.
Then if you want to still open a recordset you can do it like this
Function GetQryAllocDebits(pAllocStart As String, pAllocEnd As String) As DAO.Recordset
Dim qdef As DAO.QueryDef
Set qdef = New DAO.QueryDef
qdef.SQL = "Select * from qryAlloc_Debits where AllocStart >= pAllocStart and pAllocEnd <= pAllocEnd"
qdef.Parameters.Refresh
qdef.Parameters("pAllocStart").Value = pAllocStart
qdef.Parameters("pAllocEnd").Value = pAllocEnd
Set GetQryAllocDebits = qdef.OpenRecordset
End Function
While a [Forms]!... reference does default to a form reference when a QueryDef is run from the GUI, it is actually just another Parameter in the query in VBA. The upshot is you don't have to recode your query/create a new one at all. Also, as #Brad mentioned, whether a parameter is in the final query of a chain of queries or not, you are able to refer to the parameter as if it is in the collection of the final query. That being the case, you should be able to use code similar to this:
Sub GetQryAllocDebits(dteAllocStart As Date, dteAllocEnd as Date)
Dim db As DAO.Database
Dim qdf As DAO.QueryDef
Dim rst As DAO.Recordset
Set db = CurrentDb()
Set qdf = db.QueryDefs("qryAlloc_Debit")
If CurrentProject.AllForms("frmReportingMain").IsLoaded Then
qdf.Parameters("[forms]![frmReportingMain]![txtAllocStart]") = [forms]![frmReportingMain]![txtAllocStart]
qdf.Parameters("[forms]![frmReportingMain]![txtAllocEnd]") = [forms]![frmReportingMain]![txtAllocEnd]
Else
qdf.Parameters("[forms]![frmReportingMain]![txtAllocStart]") = CStr(dteAllocStart)
qdf.Parameters("[forms]![frmReportingMain]![txtAllocEnd]") = CStr(dteAllocEnd)
End If
Set rst = qdf.OpenRecordset
Do Until rst.EOF
'...do stuff here.
Loop
Set rst = Nothing
Set qdf = Nothing
Set db = Nothing
End Function
If the referenced form is open, the code is smart enough to use the referenced controls on the form. If not, it will use the dates supplied to the subroutine as parameters. A gotcha here is that the parameters did not like when I set them as date types (#xx/xx/xx#), even if the field were dates. It only seemed to work properly if I set the params as strings. It didn't seem to be an issue when pulling the values straight out of the controls on the forms, though.
I know it's been a while since this was posted, but I'd like to throw in my tuppence worth as I'm always searching this problem:
A stored query can be resolved:
Set db = CurrentDb
Set qdf = db.QueryDefs(sQueryName)
For Each prm In qdf.Parameters
prm.Value = Eval(prm.Name)
Next prm
Set rst = qdf.OpenRecordset
For SQL:
Set db = CurrentDb
Set qdf = db.CreateQueryDef("", "SELECT * FROM MyTable " & _
"WHERE ID = " & Me.lstID & _
" AND dWeekCommencing = " & CDbl(Me.frm_SomeForm.Controls("txtWkCommencing")) & _
" AND DB_Status = 'Used'")
For Each prm In qdf.Parameters
prm.Value = Eval(prm.Name)
Next prm
Set rst = qdf.OpenRecordset
This assumes that all parameter values are accessible - i.e. forms are open and controls have values.
'I have two parameters in my recordset and I was getting the "Too few parameters. Expected 2" 'error when using an OpenRecordset in MS Access vba, and this is how I got around it and IT WORKS! see the below sub routine:
'Private Sub DisplayID_Click()
'1. I created variables for my two parameter fields xEventID and xExID as seen below:
Dim db As Database
Dim rst As Recordset
Dim xEventID As Integer
Dim xExId As Integer
'2. Sets the variables to the parameter fields as seen below:
Set db = CurrentDb
xEventID = Forms!frmExhibitorEntry!txtEventID
xExId = Forms!frmExhibitorEntry!subExhibitors!ExID
'3. Set the rst to OpenRecordSet and assign the Set the variables to the WHERE clause. Be sure to include all quotations, ampersand, and spaces exactly the way it is displayed. Otherwise the code will break!exactly as it is seen below:
Set rst = db.OpenRecordset("SELECT tblInfo_Exhibitor.EventID,tblInfo_Display.ExID, tblMstr_DisplayItems.Display " _
& "FROM tblInfo_Exhibitor INNER JOIN (tblMstr_DisplayItems INNER JOIN tblInfo_Display ON tblMstr_DisplayItems.DisplayID = tblInfo_Display.DisplayID) ON tblInfo_Exhibitor.ExID = tblInfo_Display.ExID " _
& "WHERE (((tblInfo_Exhibitor.EventID) =" & xEventID & " ) and ((tblInfo_Exhibitor.ExID) =" & xExId & " ));")
rst.Close
Set rst = Nothing
db.Close
'End Sub
Is it possible to check if a named field is within a record set?
EG id, field1, field2, field3 have been selected. Is it possible for VBScript to detect if field2 has been selected. I am also hoping this is possible without looping
Please assume I dont know, nor can see the actual SELECT. I need to detect this after the query has been executed.
This is how its done using a loop, I am also hoping this is possible without looping:
dim rs,field,foundField
sql = "SELECT * from table;"
set rs = conn.execute(sql)
For Each field in rs.Fields
if field.Name = "someFieldName" then
foundField = true
exit for
else
foundField = false
end if
next
TYIA
I use a similar function (in VB6) to the one proposed by bfavaretto... I'm curious why the OP says it doesn't work?
Public Function FieldExists(ByVal rs As Recordset, ByVal fieldName As String) As Boolean
On Error GoTo merr
FieldExists = rs.Fields(fieldName).name <> ""
Exit Function
merr:
FieldExists = False
End Function
This function works for me... and it doesn't return false negatives as far as I know. Also, it appears to be faster than executing a loop for fields that are included in the collection; for fields that are actually missing, the execution times of both methods seems to be equivalent.
EDIT
For VBScript, the above function would look like this:
Function FieldExists(ByVal rs, ByVal fieldName)
On Error Resume Next
FieldExists = rs.Fields(fieldName).name <> ""
If Err <> 0 Then FieldExists = False
Err.Clear
End Function
And the code posted in the question would look like:
dim rs,field,foundField
sql = "SELECT * from table;"
set rs = conn.execute(sql)
foundField = FieldExists(rs, "someFieldName")
I think you need the loop. Found this on MSDN (emphasis mine):
Most of the ASP built-in objects provide collections. Collections are
data structures similar to arrays that store strings, numbers, objects
and other values. Unlike arrays, collections expand and contract
automatically as items are retrieved or stored. The position of an
item will also move as the collection is modified. You can access an
item in a collection by its unique string key, by its index (position)
in the collection, or by iterating through all the items in the
collection.
In any case, you could try this (untested):
dim rs,field,foundField
sql = "SELECT * from table;"
set rs = conn.execute(sql)
if rs.Fields("someFieldName") then
' ... if this doesn't crash, it may return
' false negatives for columns containing null or 0
end if
I'm running an LDAP query that returns multiple entries and stores them inside a SearchResultCollection. I'm iterating over the SearchResultCollection like so:
// results is my SearchResultCollection object
foreach (SearchResult sr in results)
{
... do things to each SearchResult in here ...
}
This seems like the most logical way to do this, but loop is incredibly slow. When I step through the loop with the debugger, I find that it's the very first step of initializing the foreach loop that takes the time - the actual iterations are instantaneous.
In addition, when I view the contents of the SearchResultCollection while debugging, the watch takes just as long to load the contents of the variable.
I have a theory that the SearchResultCollection doesn't actually contain complete SearchResult objects, but rather references to entries in the Active Directory server that are then individually fetched when I iterate over the SearchResultCollection object. Can anyone confirm this theory? And is there a better (faster) way to fetch a set of LDAP entries?
I suffered from the same problem and the methodology in the post below was much quicker then my own:
http://msdn.microsoft.com/en-us/library/ms180881(v=vs.80).aspx
... to answer you question yes it seems as if you try to process the entries directly while still in the loop by using something like:
If Not UserAccount.GetDirectoryEntry().Properties("sAMAccountName").Value Is Nothing Then sAMAccountName = UserAccount.Properties("sAMAccountName")(0).ToString()
... this has a drastic impact on performance, you can get around this by adding the collection to a Dictionary within the loop and then processing the dictionary:
Dim searchResult As SearchResult
Dim dictLatestLogonDatesTemp As New Dictionary(Of String, Date)
SearchResults1 = mySearcher.FindAll()
For Each searchResult In SearchResults1
Dim propertyKey,sAMAccountName As String
Dim dteLastLogonDate As Date = Nothing
For Each propertyKey In searchResult.Properties.PropertyNames
Dim valueCollection As ResultPropertyValueCollection = searchResult.Properties(propertyKey)
For Each propertyValue As Object In valueCollection
If LCase(propertyKey) = LCase("sAMAccountName") Then sAMAccountName = propertyValue
If LCase(propertyKey) = LCase("lastLogon") Then dteLastLogonDate = Date.FromFileTime(propertyValue)
Next propertyValue
Next propertyKey
If sAMAccountName <> Nothing Then dictLatestLogonDatesTemp.Add(sAMAccountName, dteLastLogonDate)
Next searchResult
It is a bit restrictive bacause a dictionary ony has two entries but you can comma seperate other values or use a dictionary of values in the dictionary:
Dim tempDictionary As Dictionary(Of String, Dictionary(Of String, String))
Hope this helps someone!
I would like to submit that adding them to a datatable also works very well and allows for more properties than a dictionary. I went from iterating 2000 users in the searchresultscollection taking almost 2 minutes to less that 1-2 seconds. Hope this helps others.
Private Sub getAllUsers()
Dim r As SearchResultCollection
Dim de As DirectoryEntry = New DirectoryEntry(GetCurrentDomainPath)
Dim ds As New DirectorySearcher(de)
ds.SearchScope = SearchScope.Subtree
ds.PropertiesToLoad.Add("name")
ds.PropertiesToLoad.Add("distinguishedName")
ds.PropertiesToLoad.Add("objectSID")
ds.Filter = "(&(objectCategory=person)(objectClass=user))" '(!userAccountControl:1.2.840.113556.1.4.803:=2) not disabled users
PleaseWait.Status("Loading Users...")
Application.DoEvents()
r = ds.FindAll()
Dim dt As New DataTable
dt.Columns.Add("Name")
dt.Columns.Add("SID")
For Each sr As SearchResult In r
Dim SID As New SecurityIdentifier(CType(sr.Properties("objectSID")(0), Byte()), 0)
dt.Rows.Add(sr.Properties("name")(0).ToString(), SID.ToString)
Next
With lstResults
lstResults.DataSource = dt
.DisplayMember = "name"
.ValueMember = "SID"
.Items.Sort()
End With
End Sub
There may be some ways to decrease the response time:
restrict the scope of the search
use a more restrictive search filter
use a base object closer to the object(s) being retrieved.
see also
LDAP: Mastering Search Filters
LDAP: Programming practices
LDAP: Search Best Practices
Sorry, I'm sure this is something that has been covered many times, but I can't find quite what I am after.
I have a single row data table which contains various settings which are used within my web system. I have been toying with turning this into an XML document instead of the single row datatable, would that make more sense?
Anyway, so, given that this is one record, there is a field called "locations," this field contains data as follows:
locationName1,IpAddress|locationName2,IpAddress|etc
The ipAddress is just the first 5 digits of the IP and allows me to ensure that logins to certain elements (admin section managed by staff) can only be accepted when connected from a company computer (ie using our ISP) - this is a largely unnecessary feature, but stops kids I employ logging in at home and stuff!
So, as the user logs in, I can check if the IP is valid by a simple SQL query.
SELECT ips FROM settings WHERE loginLocations LIKE '%" & Left(ipAddress, 5) & " %'
What I need to be able to do now, is get the name of the users location from the dataField array.
I've come up with a few long winded looping procedures, but is there a simple way to analyse
locationName1,IpAddress1|locationName2,IpAddress2|etc
as a string and simply get the locationName where LoginIp = IpAddressX
... or am I going about this in a totally ridiculous way and should turn it into an xml file? (which will then create a whole load of other questions for you about parsing XML!!)
u can split the string in Vb.net and the send it to a query or anything
'Split the string on the "," character
Dim parts As String() = s.Split(New Char() {","c})
In SQL Server, these are the functions of interest in extracting a sub-string:
CHARINDEX
SUBSTRING
LENGTH
You can google the details about them (e.g. CHARINDEX at http://msdn.microsoft.com/en-us/library/ms186323.aspx). With these, you'll need to use computed columns in your query to extract that location name.
If it's not too late, you may want to devise a new way to layout these elements. For instance, instead of:
locationName1,IpAddress1|locationName2,IpAddress2|etc
How about
{IpAddress1,locationName1}{IpAddress2,locationName2}etc
That way you can use CHARINDEX to locate "{" & Left(ipAddress, 5); from that position, locate ","; then from that position locate the closing "}". From there it should be straightforward to use SUBSTRING to get at the locationName. Be forewarned that this will likely be a messy query (probably built from a few sub-queries, one for each position).
In the end, SpectralGhost's idea to just read in the column and do the extraction in VB is probably the way with the least hassle.
I've decided to do it this way, but would appreciate comments on efficiency.
I've split ipAddress and locationName into two database columns, within the one row, and getting the required data by comparing strings as arrays, as per the code below.
For this particular application I'm only dealing with one record, so it's pretty simple. However, further down the line, I need to product a system for monitoring product sales. from an invoices table.
Each invoice record is a row in the database with items in the invoice held similarly, [item1],[item2] etc. There is another column for quantities [qty1],[qty2] etc, prices [price1],[price2], etc. I'll need to be able to search the database for invoices in which an item number occurs (easy SQL WHERE itemList LIKE %[invNO]%) and then compare arrays to get the quantities and individual prices of each item on that invoice. Extracting these rows as arrays and locating the relevant position in these as per the code below, will work fine, but when the whole operation is looping through several hundred or thousand rows, will this become really slow?
ipList, locationList = list as comma separated string from database record field
Dim ipArray As Array = Split(ipList, ",")
Dim locationArray As Array = Split(locationList, ",")
For i = 0 To UBound(ipArray)
If Left(ipArray(i), 5) = Left(ipAddress, 5) Then
arrayPosition = i
itemFound = "True"
Exit For
End If
Next
location = locationArray(arrayPosition)
'loop through ips then get the position and make the location equal to that
If itemFound <> "True" Then
inValidIP = "True"
End If
I strongly advise that you break those our into database columns and each location is a separate row; had it been done that way in the first place, you wouldn't have the problem you have now.
But since you have it in a single row/column, why not bring that back and simply get the value from .NET?
Dim Source As String = "TestLocationA,127.0|TestLocationB,128.0|TestLocationC,129.0"
Dim Test As String = Source
Dim ToFind As String = "127.0"
Test = Test.Substring(0, Test.IndexOf(ToFind & "|") - 1)
Test = Test.Substring(Test.LastIndexOf("|") + 1)
MsgBox(Test)
OR
Public Class Form1
Private IpLocationList As New List(Of IpLocation)
Private IpToFind As String = ""
Private Class IpLocation
Public Name As String
Public IP As String
Public Sub New(ByVal FullLocation As String)
Me.Name = FullLocation.Substring(0, FullLocation.IndexOf(","))
Me.IP = FullLocation.Substring(FullLocation.IndexOf(",") + 1)
End Sub
End Class
Private Function FindIP(ByVal IpLocationItem As IpLocation) As Boolean
If IpLocationItem.IP = IpToFind Then
Return True
Else
Return False
End If
End Function
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim Source As String = "TestLocationA,127.0|TestLocationB,128.0|TestLocationC,129.0"
Dim LocationList As New List(Of String)
LocationList.AddRange(Split(Source, "|"))
For Each LocationItem As String In LocationList
IpLocationList.Add(New IpLocation(LocationItem))
Next
IpToFind = "127.0"
Dim result As IpLocation = IpLocationList.Find(AddressOf FindIP)
If result IsNot Nothing Then
MsgBox(result.Name)
End If
End Sub
End Class
enter code here
This has the benefit of loading the array one time and not needing to manually loop through arrays.
I have a *.MDB database file, and I am wondering if it is possible or recommended to work against it using LINQ in C#. I am also wondering what some simple examples would look like.
I don't know a lot about LINQ, but my requirements for this task are pretty simple (I believe). The user will be passing me a file path to Microsoft Access MDB database and I would like to use LINQ to add rows to one of the tables within the database.
What you want is a LINQ to ODBC provider, or a LINQ to JET/OLEDB provider.
Out of the box, MS doesn't make one. There may be a 3rd party who does.
Actually I recently (today) discovered that you can access an Access database with LinqToSql. It must be in the 2002 or newer format, you will not be able to drag and drop the tables to your datacontext so either manually create the objects in your dbml or you can use SQL Server Migration for Access to move it to a sql server and then drag and drop all you want. When you want to actually create the context pass it an OleDbConnection. Use your standard Jet.OLEDB.4.0 connection string on the OleDbConnection and you are good to go. Not sure of the limitation this may incurr though. I just did a quick sample and did an OrderBy without issue.
I wrote a small sample program to test this out with David's answer. You'll need to make an access database and manually create the DBML for Linq-to-SQL, as you cannot drag 'n drop them.
Inserts fail, citing Missing semicolon (;) at end of SQL statement. but queries seem to work alright.
using System;
using System.Collections.Generic;
using System.Data.OleDb;
using System.IO;
using System.Linq;
using Linq2Access.Data;
namespace Linq2Access
{
class Program
{
static readonly string AppPath = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location);
static readonly string DbPath = Path.Combine(AppPath, "Data", "database.accdb");
static readonly string DbConnString = #"Provider=Microsoft.ACE.OLEDB.12.0;Data Source='" + DbPath + "';Persist Security Info=False;";
static void Main(string[] args)
{
if (!File.Exists(DbPath))
throw new Exception("Database file does not exist!");
using (OleDbConnection connection = new OleDbConnection(DbConnString))
using (DataRepositoryDataContext db = new DataRepositoryDataContext(connection))
{
List<dbProject> projects = new List<dbProject>();
for (int i = 1; i <= 10; i++)
{
dbProject p = new dbProject() { Title = "Project #" + i };
for (int j = 1; j <= 10; j++)
{
dbTask t = new dbTask() { Title = "Task #" + (i * j) };
p.dbTasks.Add(t);
}
projects.Add(p);
}
try
{
//This will fail to submit
db.dbProjects.InsertAllOnSubmit(projects);
db.SubmitChanges();
Console.WriteLine("Write succeeded! {0} projects, {1} tasks inserted",
projects.Count,
projects.Sum(x => x.dbTasks.Count));
}
catch(Exception ex)
{
Console.WriteLine("Write FAILED. Details:");
Console.WriteLine(ex);
Console.WriteLine();
}
try
{
//However, if you create the items manually in Access they seem to query fine
var projectsFromDb = db.dbProjects.Where(x => x.Title.Contains("#1"))
.OrderBy(x => x.ProjectID)
.ToList();
Console.WriteLine("Query succeeded! {0} Projects, {1} Tasks",
projectsFromDb.Count,
projectsFromDb.Sum(x => x.dbTasks.Count));
}
catch (Exception ex)
{
Console.WriteLine("Query FAILED. Details:");
Console.WriteLine(ex);
Console.WriteLine();
}
Console.WriteLine();
Console.WriteLine("Press any key to continue...");
Console.ReadKey();
}
}
}
}
You can use a DataSet. There are linq extensions that will allow you to query the data with all that LINQ goodness we have become use to :)
eICATDataSet.ICSWSbuDataTable tbl = new eICATDataSet.ICSWSbuDataTable();
ICSWSbuTableAdapter ta = new ICSWSbuTableAdapter();
ta.Fill(tbl);
var res = tbl.Select(x => x.ProcedureDate.Year == 2010);
I have seen this question a lot and in several fora. I made a go at it and here is a complete answer for those who have been looking at it.
LinQ was not made for Access. However, many of the queries will work with Access, including delete procedure. So, according to me, there are only 2 crucial deficiencies when working with Access, which are:
not being able to save data.
not being able to drag and drop objects onto the dbml
Insert will fail with the error "missing semicolon (;)". This is because LinQ save procedure was made to save data and retrieve the primary key ID of the record saved in one go. We know that you cannot execute multiple SQL statements in Access, so that is the reason for that failure.
Update will fail with the error "record not found". An update procedure will of cause look for the record to be updated then update it. I cannot tell why it wouldn't find it, when normal LinQ query to find a record works fine.
Because there is so much benefit to use LinQ, I figured out how to work around the deficiency, while enjoy the other benefits throughout my application. This is how (NB: My codes are in VB.net, but you can convert if required):
Create the LinQ to SQL (.dbml) class to manage your LinQ against the access database, and a way to manager your save procedure. Below is the full procedures of what I created and I now work with LinQ to Access without any problems:
Add a DataGridView on a form. Add buttons for Add, Edit & Delete
Code to fill the grid:
Private Sub ResetForm()
Try
Using db As New AccessDataClassesDataContext(ACCCon)
Dim rows = (From row In db.AccountTypes
Where row.AccountTypeID > 1
Order By row.AccountTypeID Ascending
Select row).ToList()
Me.DataGridView1.DataSource = rows
End Using
Catch ex As Exception
MessageBox.Show("Error: " & vbCr & ex.ToString, "Data Error", MessageBoxButtons.OK)
End Try
End Sub
DetailForm
Code to set control values
Private Sub ResetForm()
Try
If _accountTypeID = 0 Then
Exit Sub
End If
Using db As New AccessDataClassesDataContext(ACCCon)
'Dim rows = (From row In db.AccountTypes
' Where row.AccountTypeID = _accountTypeID
' Order By row.AccountTypeID Ascending
' Select row.AccountTypeID, row.AccountType, row.LastUpdated).ToList()
Dim rows = (From row In db.AccountTypes
Where row.AccountTypeID = _accountTypeID
Select row).ToList()
For Each s In rows
Me.AccountTypeIDTextBox.Text = s.AccountTypeID
Me.myGuidTextBox.Text = s.myGuid
Me.AccountTypeTextBox.Text = s.AccountType
Me.AcHeadIDTextBox.Text = s.AcHeadID
Me.DescriptionTextBox.Text = s.Description
Me.LastUpdatedDateTimePicker.Value = s.LastUpdated
Next
End Using
Catch ex As Exception
End Try
End Sub
LinQToSQLClass
You will have to add the data objects to the dbml manually since you cannot drag and drop when using Access. Also note that you will have to set all the properties of the fields correctly in the properties windows. Several properties are not set when you add the fields.
Code to Save
Public Function SaveAccountType(Optional ByVal type As String =
"Close") As Boolean
Dim success As Boolean = False
Dim row As New AccountType
Using db As New AccessDataClassesDataContext(ACCCon)
If _accountTypeID > 0 Then
row = (From r In db.AccountTypes
Where r.AccountTypeID = _accountTypeID).ToList()(0)
If String.IsNullOrEmpty(row.AccountTypeID) Then
MessageBox.Show("Requested record not found", "Update Customer Error")
Return success
End If
End If
Try
With row
.myGuid = Me.myGuidTextBox.Text
.AccountType = Me.AccountTypeTextBox.Text
.Description = Me.DescriptionTextBox.Text
.AcHeadID = Me.AcHeadIDTextBox.Text
.LastUpdated = Date.Parse(Date.Now())
End With
If _accountTypeID = 0 Then db.AccountTypes.InsertOnSubmit(row)
db.SubmitChanges()
success = True
Catch ex As Exception
MessageBox.Show("Error saving to Customer: " & vbCr & ex.ToString, "Save Data Error")
End Try
End Using
Return success
End Function
Now replace these two lines:
If _accountTypeID = 0 Then db.AccountTypes.InsertOnSubmit(row)
db.SubmitChanges()
with something like this:
Dim cmd As IDbCommand
cmd = Me.Connection.CreateCommand()
cmd.Transaction = Me.Transaction
cmd.CommandText = query
If myGuid.Trim.Length < 36 Then myGuid = UCase(System.Guid.NewGuid.ToString())
cmd.Parameters.Add(New OleDbParameter("myGuid", row.myGuid))
cmd.Parameters.Add(New OleDbParameter("AccountType", row.AccountType))
cmd.Parameters.Add(New OleDbParameter("Description", row.Description))
cmd.Parameters.Add(New OleDbParameter("AcHeadID", row.AcHeadID))
cmd.Parameters.Add(New OleDbParameter("LastUpdated", Date.Now))
If AccountTypeID > 0 Then cmd.Parameters.Add(New OleDbParameter("AccountTypeID", row.AccountTypeID))
If Connection.State = ConnectionState.Closed Then Connection.Open()
result = cmd.ExecuteNonQuery()
cmd = Me.Connection.CreateCommand()
cmd.Transaction = Me.Transaction
cmd.CommandText = "SELECT ##IDENTITY"
result = Convert.ToInt32(cmd.ExecuteScalar())
The last part of the code above is what gets you the ID of the record saved. Personally, I usually make that an option, because I don't need it in most of the cases, so I don't need to add that overhead of fetching back data every time a record is saved, I am happy just to know a record was saved.
That is the overhead added to LinQ, which causes Insert to fail with Access. Is it really necessary to have it? I don't think so.
You may have noted that I normally put my Update and Insert procedures together, so that saves me time and has address both the Insert & Update procedures in one go.
Code for Delete:
Private Sub DelButton_Click(sender As Object, e As EventArgs) Handles DelButton.Click
Using db As New AccessDataClassesDataContext(ACCCon)
Dim AccountTypeID As Integer = Me.DataGridView1.CurrentRow.Cells(0).Value
Dim row = From r In db.AccountTypes Where r.AccountTypeID = AccountTypeID
For Each detail In row
db.AccountTypes.DeleteOnSubmit(detail)
Next
Try
db.SubmitChanges()
Catch ex As Exception
' Provide for exceptions.
MsgBox(ex)
End Try
End Using
End Sub
Now you can enjoy LinQ to Access! Happy coding :)
LINQ to SQL only works for SQL Server databases. What you need is the Microsoft Entity Framework. This makes object oriented access to your mdb. From this you can run LINQ queries.
http://msdn.microsoft.com/en-us/library/aa697427(vs.80).aspx