how can i solve this please ?
i am doing a simple database project and i have a search field i wrote the following code for searching and displaying data in DataGridView but the
Null Reference Exception keeps showing up because i'm initializing the table with nothing and yet if i don't do so i get 'Used Before Initializing warning.
the question is :how can i initialize the table properly .
Private Sub txtSearch_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtSearch.TextChanged
Dim searchText As String = txtSearch.Text
Dim matchText As String = ""
Dim rowMatch As Boolean = False
Dim foundRows As DataTable = Nothing 'this initializig causes the problem of null exception,But how can i Initialize it then?????
For Each rw As DataRow In dataSet.Tables(0).Rows
Dim cl As String = rw.Item(1).ToString ' this cell is FirstName Cell
If searchText.Length > cl.ToString.Length Then
matchText = cl.ToString
Else
matchText = cl.ToString.Substring(0, searchText.Length)
End If
'bellow it adds the Found Row (rw) to the table
If (searchText.Equals(matchText) And searchText <> "" And Not foundRows Is Nothing) Then foundRows.Rows.Add(rw)
Next
'to shows data if the search text field is not empty then show the found matching rows
If (searchText <> "") Then
contactView.DataSource = foundRows
Else ' else show the original tavle again
contactView.DataSource = dataSet.Tables(0)
End If
contactView.Refresh() 'refresh
End Sub
here is the screenshot of the form
i tried to use
Dim foundRows As DataTable = New DataTable
but it shows ArgumentException
This Row already belongs to another Table
i also tried this
but as you can see nothing works please Help !
Yes
i finally got it
i was having a problem in columns
Dim foundRows As DataTable = New DataTable("PseuContact") 'this initializig causes the problem of null exception,But how can i Initialize it then?????
foundRows.Columns.Add("ID")
foundRows.Columns.Add("First Name")
foundRows.Columns.Add("Last Name")
foundRows.Columns.Add("Phone Number")
foundRows.Columns.Add("Mobile Number")
foundRows.Columns.Add("Email Address")
initializing columns is important when declaring new table
this's been the best
Related
as the title states I am trying to compare or validate a text box entry against a list of acceptable values stored in my database. As of now I have taken the values from my database and store them in a List(of String) and I have a for loop that loops through that list and returns true if the values match, if the values do not match it will return false. Below I have attached the code I am currently working with.
Protected Sub txtSearchOC_TextChanged(sender As Object, e As EventArgs) Handles txtSearchOC.TextChanged
Dim listEType As List(Of String) = New List(Of String)
Dim eType As String = txtSearchOC.Text
Dim strResult As String = ""
lblPrefix.Text = ""
lblList.Text = ""
Dim TypeIDQuery As String = "
SELECT a.OrderCode
FROM SKU AS a
INNER JOIN EnrollmentType AS e ON a.EnrollmentTypeID = e.TypeID
INNER JOIN Enrollment AS f ON e.RecID = f.EnrollmentTypeID
WHERE f.AccountNumber = '12345';
"
Using connEType As New SqlConnection(ConfigurationManager.ConnectionStrings("WarrantyConnectionString").ToString)
Using cmdEType As New SqlCommand(TypeIDQuery, connEType)
cmdEType.Parameters.Add("#AccountNumber", SqlDbType.VarChar, 15).Value = "12345"
connEType.Open()
Using sdrEType As SqlDataReader = cmdEType.ExecuteReader
While sdrEType.Read
listEType.Add(sdrEType("OrderCode").ToString)
End While
End Using
End Using
End Using
For Each Item As String In listEType
strResult &= Item & ", "
Next
For i = 0 To listEType.Count - 1
If eType = listEType(i) Then
lblPrefix.Text = "True"
End If
If eType <> listEType(i) Then
lblList.Text = "Error"
End If
Next
'lblList.Text = strResult
End Sub
In the code I declare my list and a variable to store the text value of the text box. To verify that it pulled the appropriate values from the database I have the strResult variable and can confirm that the appropriate values are being stored.
The problem I am having has to do with the For loop I have at the bottom, when I enter in a valid value that is contained in the listEType, I get the confirmation message of "True" indicating it has matched with one of the values, but I also get the "Error" message indicating that it does not match. If I enter in a value that is not contained in the list I only get the "Error" message which is supposed to happen.
My question is, based on the code I have supplied, why would that For loop be returning both "True" and "Error" at the same time for a valid entry? Also, if there is a better way to accomplish what I am trying to do, I am all ears so to speak as I am relatively new to programming.
Well, as others suggested, a drop down (combo box) would be better.
However, lets assume for some reason you don't want a combo box.
I would not loop the data. You have this amazing database engine, and it can do all the work - and no need to loop the data for such a operation. Why not query the database, and check for the value?
Say like this:
Protected Sub txtSearchOC_TextChanged(sender As Object, e As EventArgs) Handles txtSearchOC.TextChanged
If txtSearchOC.Text <> "" Then
Dim TypeIDQuery As String = "
SELECT a.OrderCode FROM SKU AS a
INNER JOIN EnrollmentType AS e ON a.EnrollmentTypeID = e.TypeID
INNER JOIN Enrollment AS f ON e.RecID = f.EnrollmentTypeID
WHERE f.AccountNumber = #AccoutNumber;"
Using connEType As New SqlConnection(ConfigurationManager.ConnectionStrings("WarrantyConnectionString").ToString)
Using cmdEType As New SqlCommand(TypeIDQuery, connEType)
cmdEType.Parameters.Add("#AccountNumber", SqlDbType.NVarChar).Value = txtSearchOC.Text
connEType.Open()
Dim rstData As New DataTable
rstData.Load(cmdEType.ExecuteReader)
If rstData.Rows.Count > 0 Then
' we have a valid match
lblPrefix.Text = "True"
Else
' we do not have a valid match
lblPrefix.Text = "False"
End If
End Using
End Using
End If
End Sub
So, pull the data into a data table. You can then check the row count, or even pull other values out of that one row. But, I don't see any need for some loop here.
Folks- I'm relatively new to ASP.NET, and have a question that has stumped my peers-- folks much more experienced than myself.
My company created a website that uses iTextSharp to build and stream PDFs. The functionality works perfectly on my company's development and staging/test servers. The customer's functionality isn't working well, however. The customer's server streams a file where the PDF is missing the last block of data representing the EOF section. The PDF seems to build correctly, streams correctly, but when users open the PDF, the following error displays: 'There was an error opening this document. The file is damaged and could not be repaired.'
By comparing the PDFs in a text viewer (comparing the PDFs from my server vice the customer's server), I can see that the EOF section is missing from the customer's PDF. I'll also note that no errors are thrown during PDF creation, if that's helpful. To make matters more difficult, I have no access to the customer's servers, so I won't be able to interact with the systems directly.
The asp.net version is 3.5. Both of our servers (my company and the customer) are: running IIS7.5 on Server 2008R2; using iTextSharp is 5.1.2; and are configured for FIPS compatibility.
I've read dozens and dozens of posts detailing why a PDF isn't created properly, why it may not be streaming, and all things related, but I haven't seen this particular issue before. I guess what I need to know in the short-term is: 1) what can I provide to help diagnose the issue, 2) where is a good place to start looking for areas of concern?
Also, I updated to revision 5.5.3 last night; same results-- it works fine on my servers, but produces broken PDFs on the customer's server.
Code added:
Public Function BuildReport(ByVal tblReport As DataTable, _
ByRef memStream As MemoryStream, _
ByRef strErrMsg As String) As Boolean
Dim booOK As Boolean = True
strErrMsg = String.Empty
' Create document
Try
' Create writer (listens to the document and directs PDF stream)
memStream = New MemoryStream()
Dim msWriter As PdfWriter = PdfWriter.GetInstance(_document, memStream)
msWriter.CloseStream = False
'Create header
Dim ev As New itsEvents
msWriter.PageEvent = ev
' Set document metadata
_document.AddTitle(_strMetaTitle)
_document.AddSubject(_strMetaSubject)
_document.AddCreator(_strMetaApplication)
_document.AddAuthor(_strMetaAuthor)
' Open document, add document content, close document
_document.Open()
AddReportContent(tblReport)
_document.Close()
Catch ex As Exception
booOK = False
strErrMsg = ex.Message
End Try
Return booOK
End Function
Private Sub AddReportContent(ByVal tblReport As DataTable)
' Count report columns
Dim intReportColumns As Integer = 0
For Each col As DataColumn In tblReport.Columns
If ContainedInColumnMask(col.ColumnName) Then
intReportColumns += 1
End If
Next
' Build table
Dim table As PdfPTable
Dim cell As PdfPCell
Dim phrase As Phrase
If intReportColumns >= 1 Then
' Init table
table = New PdfPTable(intReportColumns)
' Add title to table
'phrase = New Phrase(_strMetaTitle, _fontLarge)
'cell = New PdfPCell(phrase)
'cell.Colspan = intReportColumns
'cell.HorizontalAlignment = 1 ' 0=Left, 1=Centre, 2=Right
'table.AddCell(cell)
' Add column headers to table
Dim i As Integer = 0
Dim intColWidth As Integer
Dim intColWidths As Integer() = New Integer(intReportColumns - 1) {}
Dim intColWidthTotal As Integer = 0
Dim strColName As String
For Each col As DataColumn In tblReport.Columns
If ContainedInColumnMask(col.ColumnName) Then
strColName = col.ColumnName
If (col.ExtendedProperties.Item("NOTEXTEXPORT") <> True) Then
If col.ExtendedProperties.Contains("FRIENDLYNAME") Then
strColName = col.ExtendedProperties.Item("FRIENDLYNAME")
End If
End If
phrase = New Phrase(strColName, _fontMedium)
cell = New PdfPCell(phrase)
cell.BorderWidth = 1
cell.BackgroundColor = iTextSharp.text.BaseColor.LIGHT_GRAY
'cell.BackgroundColor = iTextSharp.text.Color.LIGHT_GRAY
table.AddCell(cell)
intColWidth = GetColumnWidth(col, strColName, _fontMedium.Size, _fontSmall.Size)
intColWidths(i) = intColWidth
intColWidthTotal += intColWidth
i += 1
End If
Next
table.TotalWidth = intColWidthTotal
table.SetWidths(intColWidths)
' Add rows to table
For Each row As DataRow In tblReport.Rows
For Each col As DataColumn In tblReport.Columns
If ContainedInColumnMask(col.ColumnName) Then
phrase = New Phrase(SetBlankIfNothing(row.Item(col.ColumnName).ToString()), _fontSmall)
cell = New PdfPCell(phrase)
cell.BorderWidth = 0.5
table.AddCell(cell)
End If
Next
Next
Else
' Init table
table = New PdfPTable(1)
' Nothing to add to table
table.AddCell(String.Empty)
End If
' Add table to document
_document.Add(table)
End Sub
Public Sub New(ByVal strMetaTitle As String, _
ByVal strMetaSubject As String, _
ByVal strMetaApplication As String, _
ByVal strMetaAuthor As String, _
Optional ByVal strColumnMask As String = "")
GetStaticInfo()
_strMetaTitle = strMetaTitle
_strMetaSubject = strMetaSubject
_strMetaApplication = strMetaApplication
_strMetaAuthor = strMetaAuthor
_document = New iTextSharp.text.Document(_itsPage, _itsMarginLeft, _itsMarginRight, _itsMarginTop, _itsMarginBottom)
If strColumnMask <> "" And Not strColumnMask Is Nothing Then
_strColumnMask = strColumnMask
End If
End Sub
Public Sub New(ByVal strMetaTitle As String, _
ByVal strMetaSubject As String, _
ByVal strMetaApplication As String, _
ByVal strMetaAuthor As String, _
Optional ByVal strColumnMask As String = "")
GetStaticInfo()
_strMetaTitle = strMetaTitle
_strMetaSubject = strMetaSubject
_strMetaApplication = strMetaApplication
_strMetaAuthor = strMetaAuthor
_document = New iTextSharp.text.Document(_itsPage, _itsMarginLeft, _itsMarginRight, _itsMarginTop, _itsMarginBottom)
If strColumnMask <> "" And Not strColumnMask Is Nothing Then
_strColumnMask = strColumnMask
End If
End Sub
Ive looked through a few questions on here today and think I'm going round in circles.
My webform has a number of elements including username which is a drop down list (populated by a SQL statement)
On submit of the form i would like the code behind aspx.vb file run a select top 1 query and return a single row of data with 4 columns.
The returned SQL query result 4 columns would only be used later in the aspx.vb file so i want to assign each of the columns to a variable. I'm struggling with this task and assigning the variable the column result from the query.
Protected Sub submitbtn_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles submitbtn.Click
Dim connString1 As String = System.Configuration.ConfigurationManager.ConnectionStrings("ConnectionString").ToString
Dim conn As New SqlConnection(connString1)
Dim sql1 As String = ""
Dim col1h As String = ""
Dim col2r As String = ""
Dim col3title As String = ""
Dim col4UQN As String = ""
sql1 = "SELECT TOP 1 col1h,col2r,col3title, col4UNQ from tblDistinctUserOHR where colID_Username= '" + username + "' "
Dim cmd1 As New SqlCommand(sql1, conn)
'open the connection
'run the sql
'the result will always be found but in case its not some form of safety catch (the variables stay as empty strings
'assign the results to the variables
'close connections
'lots of other code
End Sub
could someone point me in the right direction to run the SQL and assign the result to the the variables. I've been reading about ExecuteScalar() and SqlDataReader but that doesn't seem to be the correct option as the only examples I've found handle a single result or lots of rows with a single column
Thanks for any samples and pointers.
Try this:
Dim da As New OleDb.OleDbDataAdapter(sql1, conn)
Dim dt As New DataTable
da.Fill(dt)
If dt.Rows.Count < 0 Then
col1h = dt.Rows(0).Item("col1h")
col2r = dt.Rows(0).Item("col2r")
col3title = dt.Rows(0).Item("col3title")
col4UQN = dt.Rows(0).Item("col4UQN")
Else
'No rows found
End If
Hello stack overflow residents! this is my first post and i'm hoping to receive some help.
I've searched but because I'm still very new, i was not able to full find/understand my answer.
I keep encountering this error:
Message: Conversion from string "" to type 'Date' is not valid. File:
~/reports/pendingshipments.aspx Function: btnExportXls_Click Stack
Trace: at
Microsoft.VisualBasic.CompilerServices.Conversions.ToDate(String
Value) at reports_default.btnExportXls_Click(Object sender, EventArgs
e) in C:\Users\jet.jones\Documents\ERIRoot\ERITitan\ERITitan.ssa\Web
Application\reports\pendingshipments.aspx.vb:line 75
Here is my code:
on App_code
**Public Function Reports_PendingShipments(ByVal intClientID As Integer, ByVal strMinDate As Date?, ByVal strMaxDate As Date?, ByVal xmlSiteID As String) As DataTable
'=================================================================================
' Author: Jet Jones
' Create date: 2013.05.28
' Description: Returns a data table with pending shipments for the sites specified
'=================================================================================
Dim objConn As New SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings("Titan").ToString)
Dim cmdGet As New SqlCommand("spReports_PendingShipments", objConn)
Dim parClientID As New SqlParameter("#ClientID", SqlDbType.Int)
Dim parMinDate As New SqlParameter("#MaxDate", IIf(Not strMinDate.HasValue, DBNull.Value, strMinDate))
Dim parMaxDate As New SqlParameter("#MaxDate", IIf(Not strMaxDate.HasValue, DBNull.Value, strMaxDate))
Dim parSiteID As New SqlParameter("#Sites", SqlDbType.Xml)
Dim objAdapter As New SqlDataAdapter(cmdGet)
Dim objTable As New DataTable
parClientID.Value = intClientID
parMinDate.Value = strMinDate
parMaxDate.Value = strMaxDate
parSiteID.Value = xmlSiteID
'set up the command object
cmdGet.Connection = objConn
cmdGet.CommandType = CommandType.StoredProcedure
'add the parameters
cmdGet.Parameters.Add(parClientID)
cmdGet.Parameters.Add(parMinDate)
cmdGet.Parameters.Add(parMaxDate)
cmdGet.Parameters.Add(parSiteID)
'open the connection
objConn.Open()
'execute the query and fill the data table
objAdapter.Fill(objTable)
'return the data table
Reports_PendingShipments = objTable
'clean up
objConn.Close()
objConn = Nothing
End Function**
my aspx.vb page calls this function this way (Get the values from the query):
objTable = Reports_PendingShipments(ucClientSearch.Value,
txtMinDate.Text, txtMaxDate.Text, strSites)
I'm passing the variable strSites because the website permissions allow for users to have access to one or more site locations, and if a report is run and the user selects "All Sites" from the dropdown, I only want to send the sites they have permissions to via XML.
If I'm missing any information please let me know!
anyone's prompt response is so greatly appreciated.
The problem is that your code is expecting empty dates to be NULL, it doesn't check for empty strings. You need something like this:
if len(strMinDate)=0 then
strMinDate = "01/01/1980"
end
Not sure what you want to default the minimum date to, but you need to add code similar to the IF statement above
Be sure to add this code prior to using the variable a few lines later...
First of all, you adding MaxDate parameter twice:
Dim parMinDate As New SqlParameter("#MaxDate", IIf(Not strMinDate.HasValue, DBNull.Value, strMinDate))
Dim parMaxDate As New SqlParameter("#MaxDate", IIf(Not strMaxDate.HasValue, DBNull.Value, strMaxDate))
And moreover, then you setting parameters values wuthout check for HasValue:
parMinDate.Value = strMinDate
parMaxDate.Value = strMaxDate
Remove these lines and fix min date parameter name
Note: This code actually codes from a tutorial book I'm reading at the moment, so you can imagine this is frustrating me greatly! I'm building a basic shopping cart, using VB.NET 4, Visual Studio 2010 and MS SQL Server R2 2008. The code below is supposed to remove items from the cart, by reading a session variable, editing it to remove the appropriate ProductID and return the amending string to the session variable. It is then supposed to rebind the data to the gridview (gvCart) to refresh the data...but it seems here there is an error.
Every time I build the site in Visual Studio, it validates fine. But every time I run the site, and attempt to use the remove button it gives me the error:
Incorrect syntax near ')'.
with the IDE pointing me toward the final parenthesis.
I have been pulling my hair out at this for a good 4 hours now, any advice appreciated!
Protected Sub gvCart_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles gvCart.SelectedIndexChanged
'This method is hooked to the Remove button & is removing items from the cart
Dim strProductId As String = gvCart.SelectedRow.Cells(1).Text
If Session("Cart") IsNot Nothing Then
'Remove selected ProductID from Session string and retrieve session string
Dim strCart As String = Session("Cart").ToString()
Dim arIDs As String() = strCart.Split(",")
'Iterate through ID's in the 'Cart' array and rebuild the string leaving out the selected ID
strCart = String.Empty
For Each str As String In arIDs
'use Trim to remove leading and trailing spaces
If str.Trim() <> strProductId.Trim() Then
strCart += str + ", "
End If
Next
'Remove trailing space and comma
If strCart.Length > 1 Then
strCart = strCart.Trim()
strCart = strCart.Substring(0, strCart.Length - 1)
End If
'Put back into session var
Session("Cart") = strCart
'Rebind gvCart, which forces the sqldatasource to requery
gvCart.DataBind()
End If
End Sub
[EDIT]
I am also including the code that runs for the event sqlCart_Selecting for completion sake:
Protected Sub sqlCart_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceSelectingEventArgs) Handles sqlCart.Selecting
Trace.Warn("sqlCart_Selecting") 'aids debugging
Dim strCart As String = String.Empty
If Session("Cart") IsNot Nothing Then
strCart = Session("Cart").ToString
e.Command.CommandText &= " WHERE product.ProductID IN (" + strCart + ") AND culture.CultureID = 'en'"
Else
e.Cancel = True
End If
End Sub
[EDIT]
Also including the SQL query used by the gridview 'gvCart' and the code for displaying the carts contents on another page
<asp:SqlDataSource ID="sqlCart" runat="server" ConnectionString="<%$ ConnectionStrings:AdventureWorksConnectionString %>" SelectCommand="SELECT product.ProductID, product.Name, product.ProductNumber, product.Color, subcat.Name AS SubcategoryName, cat.Name AS CategoryName, description.Description FROM Production.Product product JOIN Production.ProductSubcategory subcat ON product.ProductSubcategoryID = subcat.ProductSubcategoryID JOIN Production.ProductCategory cat ON subcat.ProductCategoryID = cat.ProductCategoryID JOIN Production.ProductModel model on product.ProductModelID = model.ProductModelID JOIN Production.ProductModelProductDescriptionCulture culture ON model.ProductModelID = culture.ProductModelID JOIN Production.ProductDescription description ON culture.ProductDescriptionID = description.ProductDescriptionID"></asp:SqlDataSource>
Protected Sub btnAddToCart_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAddToCart.Click
'The contents of the cart will be saved in a Session object as a string of coma-delimited values of ProductID's
Dim strCart As String = String.Empty
Dim strProductID As String = gvProducts.SelectedDataKey.Value.ToString()
If Session("Cart") Is Nothing Then
strCart = strProductID
Else
strCart = Session("Cart").ToString() + ", " + strProductID
End If
Session("Cart") = strCart
lblCart.Text = strCart
End Sub
I will take a shot here, since you are not showing us everything (the SQL query for instance).
But it feels like the SQL query is using IN clause. And it appears to be failing when the cart goes empty.
Since Session("Cart") contains the comma separated values of the product IDs, an empty list would make the following SQL query fail:
select id, name
from products
where id in ()
with the message:
Incorrect syntax near ')'.
You have to show us the portion of code that's reloading the query from Session("Cart"). The query should be reassembled.
But there's one trick you can use! If your product ids are numeric and always greater than zero, change this line:
strCart = String.Empty
to this:
strCart = '-1, '
Update
I will really teach how to fish on this one. :) the problem is here:
Dim strCart As String = String.Empty
If Session("Cart") IsNot Nothing Then
strCart = Session("Cart").ToString
e.Command.CommandText &= " WHERE product.ProductID IN (" + strCart + ") AND culture.CultureID = 'en'"
Else
e.Cancel = True
End If
When cart is empty, Session("Cart") is not Nothing but it's an empty string (provided that you removed the -1 workaround). If Session("Cart") is an empty string the where clause should be " WHERE culture.CultureID = 'en'" only, no mention to product ids. God speed!