I am trying to learn how to do this .NET frameworks for my job and what not….. I can’t figure why it isn’t working.
Error occurs here:
myCommand.Connection.Open()
I am assuming it is because of how I am doing….
Dim idbox As TextBox = E.Item.Cells(numCols - 1).Controls(0)
myCommand.Parameters("@Id").Value = Integer.Parse(idbox.Text)
Source:
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Data.OleDb" %>
<html>
<script language="VB" runat="server">
Dim myConnection As SqlConnection
' Create a connection to the "pubs" SQL database located on the
' local computer.
Sub Page_Load(Src As Object, E As EventArgs)
If Session("Admin") <> True Then
Response.Redirect("login.aspx")
Else
Dim myConnection As SqlConnection = New SqlConnection("CONNECTION INFO")
' Determine whether this page is a postback. If it is not a
' postback, call BindGrid.
If Not IsPostBack Then
Dim dbconn As OleDbConnection
Dim sql As String
Dim dbcomm As OleDbCommand
Dim dbread As OleDbDataReader
dbconn = New OleDbConnection("CONNECTION INFO")
dbconn.Open()
sql = "SELECT Name FROM TestData"
dbcomm = New OleDbCommand(sql, dbconn)
dbread = dbcomm.ExecuteReader()
DropDownList1.Items.Clear()
While dbread.Read
DropDownList1.Items.Add(dbread(0))
End While
dbread.Close()
dbconn.Close()
BindGrid()
End If
End If
End Sub
' Create an index to the DataGrid row that is clicked and
' call BindGrid.
Sub MyDataGrid_Edit(sender As Object, E As DataGridCommandEventArgs)
MyDataGrid.EditItemIndex = CInt(E.Item.ItemIndex)
BindGrid()
End Sub
' Cancel resets the index to the row's previous settings.
Sub MyDataGrid_Cancel(sender As Object, E As DataGridCommandEventArgs)
MyDataGrid.EditItemIndex = -1
BindGrid()
End Sub
' When the Update link is clicked, build a SQL UPDATE command,
' connect to the database, update the row's information in the
' database, and rebind the DataGrid to show the updated information.
Public Sub MyDataGrid_Update(sender As Object, _
E As DataGridCommandEventArgs)
Dim updateCmd As String = "UPDATE TestData SET AdoptedNum = @AdoptedNum, PrecinctNum = @PrecinctNum WHERE Id = @Id"
Dim myCommand As SqlCommand = New SqlCommand(updateCmd, myConnection)
myCommand.Parameters.Add(New SqlParameter("@Name", SqlDbType.VarChar))
myCommand.Parameters.Add(New SqlParameter("@PrecinctNum", SqlDbType.Int))
myCommand.Parameters.Add(New SqlParameter("@AdoptedNum", SqlDbType.Int))
myCommand.Parameters.Add(New SqlParameter("@Id", SqlDbType.Int))
' Initialize the SqlCommand "@ID" parameter to the ID of the row
' that must be clicked.
Dim numCols As Integer = E.Item.Cells.Count
Dim i As Integer
Dim colvalue As String
Dim txtBox As TextBox
Dim idbox As TextBox = E.Item.Cells(numCols - 1).Controls(0)
myCommand.Parameters("@Id").Value = Integer.Parse(idbox.Text)
' Create an array of column names.
Dim cols() As String = {"@Name", "@PrecinctNum", "@AdoptedNum", "@Id"}
' Skipping the first, second, and last columns, iterate through the
' columns, checking for empty values. If an empty value is found,
' display a message box. Also initialize the SqlCommand
' parameter values.
For i = 2 To numCols - 1
txtBox = E.Item.Cells(i).Controls(0)
colvalue = txtBox.Text
If (i < numCols And colvalue = "") Then
Message.InnerHtml = "ERROR: Null values not allowed for " _
& "Author ID, Name or Phone"
Message.Style("color") = "red"
Exit Sub
End If
myCommand.Parameters(cols(i - 1)).Value = colvalue
Next i
' Connect to the database and update the information.
myCommand.Connection.Open()
' Test whether the data was updated, and display the
' appropriate message to the user.
Try
myCommand.ExecuteNonQuery()
Message.InnerHtml = "<b>Record Updated.</b><br>"
MyDataGrid.EditItemIndex = -1
Catch ex As SqlException
If ex.Number = 2627 Then
Message.InnerHtml = "ERROR: A record already exists" _
& " with the same primary key"
Else
Message.InnerHtml = "ERROR: Could not update record," _
& " please ensure the fields are correctly filled out."
Message.Style("color") = "red"
End If
End Try
' Close the connection.
myCommand.Connection.Close()
' Rebind the DataGrid to show the updated information.
BindGrid()
End Sub
' The BindGrid procedure connects to the database and implements
' a SQL SELECT query to get all the data in the "Authors" tablea.
Public Sub BindGrid()
Dim myConnection As SqlConnection = _
New SqlConnection("CONNECTION INFO")
Dim myCommand As SqlDataAdapter = New SqlDataAdapter("SELECT *" _
& " FROM TestData WHERE Name='" & DropDownList1.SelectedValue & "'", myConnection)
Dim ds As DataSet= New DataSet()
myCommand.Fill(ds)
MyDataGrid.DataSource = ds
MyDataGrid.DataBind()
End Sub
Protected Sub MyDataGrid_SelectedIndexChanged(sender As Object, e As System.EventArgs)
End Sub
Sub DropDownList1_SelectedIndexChanged(sender As Object, e As EventArgs)
BindGrid()
End Sub
</script>
<body style="font: 10pt verdana">
<form id="Form1" runat="server"><center>
<h3><font face="Verdana">Updating a Row of Data.</font></h3>
<span id="Message" EnableViewState="false"
style="font:arial 11pt;" runat="server"/><p>
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>
<ASP:DataGrid id="MyDataGrid" runat="server"
Width="800"
BackColor="#ccccff"
BorderColor="black"
ShowFooter="false"
CellPadding=3
CellSpacing="0"
Font-Name="Verdana"
Font-Size="8pt"
HeaderStyle-BackColor="#aaaadd"
OnEditCommand="MyDataGrid_Edit"
OnCancelCommand="MyDataGrid_Cancel"
OnUpdateCommand="MyDataGrid_Update"
>
<Columns>
<ASP:EditCommandColumn EditText="Edit" CancelText="Cancel"
UpdateText="Update"/>
</Columns>
</ASP:DataGrid>
</center>
</form>
</body>
</html>
I suspect the problem is you define but never initialize the instance variable myConnection. You define and instantiate a local variable of the same name within the Page_Load function, but that is a distinct and different object than your instance variable.
In your Page_Load, if you change this:
to this:
then your instance variable should be initialized and ready for use in your MyDataGrid_Update event handler.