How do you update a single field in an Access database using an asp.net website in VisualStudio08. Assuming that the connection has been established, give step to step instructions of what to do in the design view.
Here is a console app that shows you how to use ADO.NET to update an Access DB.
An alternate is to use Linq.
You could add a method to your CodeBehind that does something like this, and call it from your OnClick event handler.
Option Explicit On
Option Strict On
Imports System
Imports System.Data
Imports System.Data.OleDb
Public Class Program
Public Shared Sub Main()
Dim connectionString As String = GetConnectionString()
Dim queryString As String = _
"UPDATE Categories Set CategoryName = 'ABC' WHERE CategoryID = 1;"
Using connection As New OleDbConnection(connectionString)
Dim command As OleDbCommand = connection.CreateCommand()
command.CommandText = queryString
Try
connection.Open()
Dim rowsAffected As Integer = command.ExecuteNonQuery()
Catch ex As Exception
Console.WriteLine(ex.Message)
End Try
End Using
End Sub
Private Shared Function GetConnectionString() As String
' To avoid storing the connection string in your code,
' you can retrieve it from a configuration file.
' Assumes Northwind.mdb is located in c:\Data folder.
Return "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" _
& "c:\Data\Northwind.mdb;User Id=admin;Password=;"
End Function
End Class
Assuming you want this done on some postback event like a button click, you need to (this is from memory, I don't have it in front of me!):
click on the button, show its properties, then the events tab.
double-click in the OnClick space to create a new event handler (or enter a name directly)
In the event handler in the code window, invoke some SQL something like
update table set field=value where field2=identifier
(or you could use the LINQ equivalent) Where table, field, field2, value and identifier should be replaced with specific names to suit your database.
You could create a SqlCommand::ExecuteNonQuery instance to run the SQL.
Related
Here is the code, but the datatable is NULL in ButtonExport click event, how can i pass the DataTable to Sub ButtonExport_Click ? I dont want to store in Session as the data is too big
Here is the class clsGlobalVarriable
Public Class clsGlobalVariable
Private _gdt As DataTable
Public Property globalDataTable As DataTable
Get
Return _gdt
End Get
Set(ByVal value As DataTable)
_gdt = value
End Set
End Property
End Class
Here is the From frmTest code:
Public Class frmTest
Inherits System.Web.UI.Page
Private gdt As New clsGlobalVariable
Protected Sub ButtonInactivePC_Click(sender As Object, e As EventArgs) Handles ButtonInactivePC.Click
Try
Dim func As New clsFunction
Dim command As String = "Get-ADComputer -Filter { OperatingSystem -NotLike '*Windows Server*'} -Property * | select Name, CanonicalName, operatingSystem, LastLogonDate, Description, whenChanged | Where {($_.LastLogonDate -lt (Get-Date).AddDays(-90)) -and ($_.LastLogonDate -ne $NULL)}"
Dim arr As New ArrayList
arr.Add("Name")
arr.Add("CanonicalName")
arr.Add("operatingSystem")
arr.Add("LastLogonDate")
arr.Add("whenChanged")
arr.Add("Description")
gdt.globalDataTable = func.PSObjectToDataTable(command, arr)
Me.GridView1.DataSource = gdt.globalDataTable
Me.GridView1.DataBind()
Catch ex As Exception
Me.LabelDebug.Text = "Button Click" + ex.Message
End Try
End Sub
Protected Sub ButtonExport_Click(sender As Object, e As EventArgs) Handles ButtonExport.Click
Dim func As New clsFunction
Dim dt As New DataTable
dt = (DirectCast(Me.GridView1.DataSource, DataTable))
Me.LabelDebug.Text = "Global Data Table Count = " & dt.Rows.Count
End Sub
When working with webpages that show data to the user, and the user takes some action on that data you either need to store the data somewhere in their computer, your computer (the server) or rely on the fact that it's still stored in the computer you got it from. As a process you have undertaken:
You generate a grid from querying AD
You send the grid to the customer's computer - so it's stored there as a visual representation (and maybe also ViewState)
It's still stored in AD, where you got it
You could also store it locally on the server somehow - Session, DB, text file, whatever
Decide on which of these to use when the user clicks Export:
Dig it out of the viewstate or other data that was sent to the user - for this you'll have to code things up so it comes back from the user
Get it out of AD again - simple to do; you did it once and sent it to the user in HTML. Getting it again and sending it to the user again this time as a CSV isn't really any different from the first time you did it
Restore it from wherever you kept it on the server
Choose the first if your user is going to modify the data or choose to export only some of it - the data he sends back to you should indicate which bits he wants exporting.
Choose the second option if you want an easy life, and it's just a straight export, no editing or subset of data. Write one method that gets the data out of AD and then use it in either place, one to form HTML/fill a grid, in the other to send a file to the user. Don't get hung up on "well I already got this data once, it's a waste to get it again" - no-one writes a Login Page and thinks "i'll only ever look up a user from the DB once, then get the server to remember the login data forever more and use it next time there is a login request" - they store the data in the db, and look it up every time there is a login. DBs store data and perform the same queries over and over again. This is no different
You probably wouldn't choose the third option, for reasons already mentioned
I decided to use alternative for the Excel Export, i am not going to pass the DataTable, instead i pass the GridView to the Export to Excel function
Add the following sub right after Page_load, this is to avoid the GridView error
Public Overrides Sub VerifyRenderingInServerForm(ByVal control As Control)
End Sub
Here is the Code:
Public Sub ExportFromGridview(ByVal gv As GridView, ByVal response As HttpResponse
response.Clear()
response.Write("<meta http-equiv=Content-Type content=text/html;charset=utf-8>")
response.AddHeader("content-disposition", "attachment;filename=" & Now & ".xls")
response.ContentType = "application/vnd.xls"
Dim stringWrite As System.IO.StringWriter = New System.IO.StringWriter()
Dim htmlWrite As System.Web.UI.HtmlTextWriter = New HtmlTextWriter(stringWrite)
gv.RenderControl(htmlWrite)
response.Write(stringWrite.ToString())
response.End()
End Sub
We would like to update data in a SQL Server 2012 database with a value obtained from
changing a value on an ASP.Net DetailsView. I Would would like to update the database using
a strongly typed DataSet called DataSetParentsDetails
a TableAdapter called ParentsDetailsTableAdapter
a DataTable called ParentsDetails.
These were created with the DataSet Designer.
This is the code from the code-behind file used to figure out the amount we want to update into the database:
Protected Sub DetailsViewDetails_ItemCommand(sender As Object, e As System.Web.UI.WebControls.DetailsViewCommandEventArgs)
Dim dcmAmountToAdjust As Decimal
Dim StrSqlStatement As String
Select Case e.CommandName
Case "Add"
Case "Edit"
dcmOriginalRegistrationFee = GetValueFromLabelRegistrationFee()
Case "Delete"
Case "Update"
dcmNewRegistrationFee = GetValueFromTextBoxRegistrationFee()
dcmAmountToAdjust = dcmNewRegistrationFee - dcmOriginalRegistrationFee
' Update the tuition balance in the parent's data.
'-------------------------------------------------
StrSqlStatement =
"Update Students " & _
"Set RegistrationCode = RegistrationCode + #AmountToAdjust " & _
"Where StudentID = #ID"
' Code to update the database goes here.
'---------------------------------------
End Select
End Sub
I'm sure that this was asked many times before but I can't find a good example on how to use the query in: StrSqlStatement to update the database through the strongly typed DataSet.
First off you need a connection string, it's good practise to store your connection strings in the web.config file:
<connectionStrings>
<add name="MyConnectionString" connectionString="Data Source=putYourServerAndInstanceNameHere;Initial Catalog=putYourDatabaseNameHere;User ID=putYourSqlUsernameHere;Password=password" providerName="System.Data.SqlClient" />
</connectionStrings>
This is a direct child of the root <configuration> element. For more information about connection strings, visit http://www.connectionstrings.com.
Then you'll need some imports in your code-behind, and you'll need to add them as references to your project if you haven't already got them in there:
Import System.Data
Import System.Data.SqlClient
Then we connect to the database and run our command, we use parameters because they're more secure.
'build the connection object using the string from the web.config file
Using conn As New SqlConnection(ConfigurationManager.ConnectionStrings("MyConnectionString").ConnectionString)
'build the command object specifying the command text and the connection to use, conn
Using cmd As New SqlCommand("UPDATE Students SET RegistrationCode = RegistrationCode + #AmountToAdjust WHERE StudentID = #ID", conn)
'add the parameters needed by the command
cmd.Parameters.AddWithValue("#AmountToAdjust", amountToAdjust)
cmd.Parameters.AddWithValue("#ID", studentID)
'try to open the connection and execute the statement
Try
conn.Open()
cmd.ExecuteNonQuery()
Catch ex As Exception
'handle the exception here
End Try
End Using
End Using
Note that there is no need to use conn.Close() here as the Using statement will take care of that for you (SqlConnection's Dispose method closes the connection if it is still open).
I have been trying to apply a solution to some functionality that a user requires on their system.
A user requires me to implement a locking system on their system. They have multiple users which may require to access the site, but the user would like the ability for them to independently lock a records in the web site site, for them to add notes to and to then unlock this so other users are able to do the same.
I have a button on my web page simply named btnLock and i have added an additional column in my database called LockedBy and have the following stored procedure...
ALTER PROCEDURE LockWeeklyTest
(
#AgendaID BIGINT,
#LockingUser VARCHAR(20)
)
AS
BEGIN
SET NOCOUNT ON
UPDATE
WeeklyAgenda
SET
LockedBy = #LockingUser
WHERE
AgendaID = #AgendaID
AND
LockedBy IS NULL
END
I have a class named Weekly Class and have the following code...
Public Shared Sub LockWeeklyAgenda(ByVal WeeklyClass As WeeklyClass)
Using dbConnection As New SqlConnection(ConfigurationManager.AppSettings("dbConnection"))
dbConnection.Open()
Dim dbTrans As SqlTransaction
dbTrans = dbConnection.BeginTransaction()
Using dbCommand As SqlCommand = dbConnection.CreateCommand
With dbCommand
.Transaction = dbTrans
.CommandType = CommandType.StoredProcedure
.CommandText = "LockWeeklyTest"
'Add Parameters for Update
.Parameters.AddWithValue("#AgendaID", WeeklyClass.AgendaID)
.Parameters.AddWithValue("#LockingUser", WeeklyClass.LockedBy)
dbCommand.ExecuteNonQuery()
End With
End Using 'dbCommand
dbTrans.Commit()
End Using
End Sub
I was thinking that the below code for the butlock would populate my Loggedby field with the username but this isnt the case.
Protected Sub btnLock_Click(sender As Object, e As System.EventArgs) Handles btnLock.Click
Dim lock As New WeeklyClass
If lock.LockedBy = "Null" Then
lock.LockedBy = System.Environment.UserName
'lock.AgendaID = AgendaID
End If
' save to the database using the Class DAL
WeeklyClassDAL.LockWeeklyAgenda(lock)
End Sub
I know that the Stored Procedure works as i have tested with the following statement as an example...
EXEC LockWeeklyTest 11, 'Betty'
Im sure that its something to do with the btnlock_click, but im not 100% sure what this is.
Any help is much appriechiated.
Your problem is this line:
If lock.LockedBy = "Null" Then
"Null" is actually a string containing the word Null. What you're after is:
If String.IsNullOrEmpty(lock.LockedBy) Then
That way, if it is actually null or empty, your LockedBy will be set. Currently, it's only setting the LockedBy if LockedBy already equals the string value "Null", which it won't directly after being declared. Is this logic really necessary considering LockedBy will always be null directly after you've declared the WeeklyClass?
Something doesn't look quite right with the AgendaID:
During the button click event the value has been commented out but is still passed through to the stored procedure inside the data layer's 'LockWeeklyAgenda' method.
It's also not defined as a nullable parameter inside the stored procedure itself, so the value that's being sent would depend on the WeeklyClass class' constructor..
can you please also show how the WeeklyClass code looks like?
I'm new to Entity Framework and am expanding an existing codebase. I'm using jQuery to pass the needed info back to the server ajaxy style, so I can't use TryUpdateModel(). Here's the code:
<HttpPost()>
Function UpdateRoster() As JsonResult
Dim model As New Models.ViewModels.PlayerAdmin
Dim jsonString As String = Request.Form("json")
model = Deserialise(Of Models.ViewModels.PlayerAdmin)(jsonString)
For Each playerAdminPlayer As Models.ViewModels.PlayerAdminPlayer In model.Roster
Dim playerToTeam As New DAL.PlayersToTeam
Dim player As DAL.Player = PlayerAdminManager.GetPlayerById(playerAdminPlayer.PlayerId)
player.FirstName = playerAdminPlayer.FirstName
PlayerAdminManager.SaveChanges()
Next playerAdminPlayer
Dim playerAfter As DAL.Player = PlayerAdminManager.GetPlayerById(model.Roster.First.PlayerId)
Return Json(New With {.success = False, .message = playerAfter.FirstName})
End Function
Deserialise is a helper function that converts the incoming JSON string to a vb object.
Things seem to work fine in that player successfully loads from the DB and playerAdminPlayer is the correct object from the JSON string. However, when I call PlayerAdminManager.SaveChanges() (which just passes the call the db.SaveChanges() the result is always 0, even if there is a change (not sure if that is expected).
playerAfter was my attempt to see if changes were actually being saved. It seems to work correctly, in that playerAfter.FirstName is the newly updated first name.
PlayerAdminManager.GetPlayerById(integer) pulls from the DB, so I would think that, since changes are observed in playerAfter, that those changes were saved to the DB. However, when I reload the web page (which pulls from the DB), the old values are there.
Any ideas?
Here are some of the functions I mention:
Function GetPlayerById(ByVal Id As Integer) As DAL.Player
Return Container.Players.Where(Function(o) o.PlayerId = Id And o.IsVisible = True).SingleOrDefault
End Function
Sub SaveChanges()
Dim numberOfChanges As Integer = Container.SaveChanges()
Debug.WriteLine("No conflicts. " & numberOfChanges.ToString() & " updates saved.")
End Sub
EDIT
Container code:
Private _Container As DAL.LateralSportsContainer
Protected ReadOnly Property Container As DAL.LateralSportsContainer
Get
If _Container Is Nothing Then
Dim connStr As New System.Data.EntityClient.EntityConnectionStringBuilder
connStr.ProviderConnectionString = Web.Configuration.WebConfigurationManager.ConnectionStrings("ApplicationServices").ConnectionString
connStr.Metadata = "res://*/Lateral.csdl|res://*/Lateral.ssdl|res://*/Lateral.msl"
connStr.Provider = "System.Data.SqlClient"
_Container = New DAL.LateralSportsContainer(connStr.ConnectionString)
End If
Return _Container
End Get
End Property
Turns out I was using a non static (shared) Container. I had 2 Manager classes that both inherited from a BaseManager class were the Container was defined. I was executing the query command in one Manager and saving in another.
Doh!
I know my ASP.NET but i have to admit, i am dumb with classes and not sure how they work exactly. Also have not worked with them yet but i want to. But what I do know is that it's a place where i can keep code for re-use correct? How will my class look with my code?
So this is my code i use on about 3 forms - but i want to save it in 1 spot and just call it from like when i click on btnSubmit.
Dim strConnection As String = ConfigurationManager.ConnectionStrings("ConnectionString").ConnectionString
Dim con As SqlConnection = New SqlConnection(strConnection)
Dim cmd As SqlCommand = New SqlCommand
Dim objDs As DataSet = New DataSet
Dim dAdapter As SqlDataAdapter = New SqlDataAdapter
cmd.Connection = con
cmd.CommandType = CommandType.Text
cmd.CommandText = "SELECT distinct FIELD FROM TABLE order by FIELD"
dAdapter.SelectCommand = cmd
con.Open()
dAdapter.Fill(objDs)
con.Close()
If (objDs.Tables(0).Rows.Count > 0) Then
lstDropdown.DataSource = objDs.Tables(0)
lstDropdown.DataTextField = "FIELD"
lstDropdown.DataValueField = "FIELD"
lstDropdown.DataBind()
lstDropdown.Items.Insert(0, "Please Select")
lstDropdown2.Items.Insert(0, "Please Select")
Else
lblMessage.Text = "* Our Database seem to be down!"
End If
What must i put here to execute my code above?
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
?????????????????????????????????
End Try
End Sub
Etienne
A class is (in VB.Net) is defined as so
Public Class Person
private _firstName as string
private _lastName as string
'''Constructor with no params
public Sub New()
_firstName = ""
_lastName = ""
End Sub
'Contructor with params
Public Sub New(FirstName as String, LastName as String)
_firstName = FirstName
_lastName = LastName
End Sub
Public Property FirstName As String
Get
return _firstName
End Get
Set(value as String)
_firstName = value
End Set
End Property
Public Property LastName As String
Get
return _lastName
End Get
Set(value as String)
_lastName = value
End Set
End Property
Public Function HitHomeRun() As Boolean
....'Do some stuff here
End Function
End Class
You can then instantiate the class and call its members.
Dim p as New Person()
p.FirstName = "Mike"
p.LastName = "Schmidt"
dim IsHomeRunHit As Boolean = p.HitHomeRun()
Learn more about creating and consuming classes in VB.Net.
This is a very big topic and can be defined in many different ways. But typically what you are venturing into is an N-Tier architecture.
Data Access Layer
Business Logic
UI Logic
Now the way a class can be built in your question can be done, but in the long run is prone to maintenance horror and modifiiability is cut short. Not to mention very much prone to bugs. Putting any type of data access code in your UI layer is bad practice.
This is where the power of having separate layers of classes (separation of concerns) in each layer gives you the ability to reuse code and ability to easily modify for future expansions/features etc. This is getting into Software Architecture is a very broad topic to put into one post.
But if you are really interested here are some links to point you into the right directions.
N-Tier Architecture from Wikipedia
Data Access Layer
Business Logic Layer
Martin Fowler is an expert in Architecture
There is software that eases the pain of the DAL.
1. Linq-To-SQL ability to query your data via .Net Objects (compiled queries)
2. Entity Framework Version 2 of Linq-To-SQL
And this effectively could replace all of your SQL code.
If you want to reuse the code, you should put it in a separate project. That way you can add that project to different solutions (or just reference the compiled dll).
In your web project you add a reference to the project (or to the dll if you have compiled it before and don't want to add the project to the solution).
In your new project you add a class file, for example named UIHelper. In the class skeleton that is created for you, you add a method. As the class is in a separate project, it doesn't know about the controls in the page, so you have to send references to those in the method call:
Public Shared Sub PopulateDropdowns(lstDropdown As DropDownList, lstDropdown2 As DropDownList)
... here goes your code
End Sub
In your page you call it with references to the dropdown lists that you have in the page:
UIHelper.PopulateDropdowns(lstDropdown, lstDropdown2)
This will get you started. There is a lot more to learn about using classes...
I sometimes create a "Common" class and put public Shared methods in it that I want to call from different places.
Something along these lines:
Public Class Common
Public Shared Sub MyMethod
'Do things.
End Sub
End Class
I'd then call it using:
Common.MyMethod
Obviously, you can a sub/function definition that takes the parameters you require.
Sorry if my VB.NET code is a bit off. I usually use C#.
I think you should look into using visual studio designer tools to do your data access and data binding. Search for typed datasets