Hi,
I’m new to asp.net. I want to create an asp.net page that allows user to
edit the data. I have pasted my code below. I am able to display the data in
a datagrid. At the bottom of the page there are two buttons “Save Changes”
and “Cancel”. When “Save Changes” button is clicked saveRec function is
called. But for some reason inside saveRec function the value of the textbox
is not visible. The line
Label2.Text = txtFirstName.Text
give an error -- System.NullReferenceException: Object reference not set to
an instance of an object.
Thanks for your help.
Joe
<%@ Page Language="VB" Debug="true" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.OleDb" %>
<!-- #include file=dsn.aspx -->
<script language="VB" runat="server" >
Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
If Not Page.IsPostBack Then
' Save the referrer Url
ViewState("ReferrerUrl") = Request.UrlReferrer.ToString()
BindData()
End If
End Sub
Sub BindData()
dim strsql as string
'check for an id
If Request.QueryString.Item("id") Is Nothing Then
response.redirect("Resultslist.aspx")
Else
strsql="select * from [Results] where [ID]=" &
request.querystring("id")
End If
'Create a connection string
Dim connString as String
connString = getdsn()
'Open a connection
Dim objConnection as OleDbConnection
objConnection = New OleDbConnection(connString)
objConnection.Open()
'Create a command object
Dim objCommand as OleDbCommand
objCommand = New OleDbCommand(strSQL, objConnection)
'Get a datareader
Dim objDataReader as OleDbDataReader
objDataReader =
objCommand.ExecuteReader(CommandBehavior.CloseConn ection)
'Do the DataBinding
myDataGrid.DataSource = objDataReader
myDataGrid.DataBind()
'Close the datareader/db connection
objDataReader.Close()
End Sub
Sub saveRec(Sender As Object, e As System.EventArgs)
'Dim txtFirstName As System.Web.UI.WebControls.TextBox
'Dim txtLastName As System.Web.UI.WebControls.TextBox
'Dim txtCity As System.Web.UI.WebControls.TextBox
dim strSQL as string
'check for an id
If Request.QueryString.Item("id") Is Nothing Then
response.redirect("Resultslist.aspx")
Else
strSQL="Update Results set first_name=@fn, last_name=@ln,
city=@ct where ID=" & request.querystring("id")
End If
'Create a connection string
Dim connString as String
connString = getdsn()
'Open a connection
Dim objConnection as OleDbConnection
objConnection = New OleDbConnection(connString)
objConnection.Open()
'Create a command object
Dim objCommand as OleDbCommand
objCommand = New OleDbCommand(strSQL, objConnection)
objCommand.Parameters.Add("@fn", OleDbType.VarChar, 255)
objCommand.Parameters.Add("@ln", OleDbType.VarChar, 255)
objCommand.Parameters.Add("@ct", OleDbType.VarChar, 255)
objCommand.Parameters("@fn").Value = txtFirstName.Text
objCommand.Parameters("@ln").Value = txtLastName.Text
objCommand.Parameters("@ct").Value = txtCity.Text
Try
Label2.Text = txtFirstName.Text
' Execute the command
'objCommand.ExecuteNonQuery()
'myDataGrid.DataBind()
Catch Ex as Exception
Response.Write("<p><strong>An Error Occurred:</strong> " & Ex.ToString()
& "</p>" & vbCrLf)
Finally
objConnection.Close()
End Try
End Sub
Sub cancel(Sender As Object, e As EventArgs)
Response.Redirect(ViewState("ReferrerUrl").ToStrin g())
End Sub
</script>
<body>
<html>
<head>
<title>Untitled</title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<asp:datagrid id="myDataGrid"
runat="server"
AutoGenerateColumns="False"
width="80%">
<ItemStyle Font-Size="X-Small"></ItemStyle>
<HeaderStyle Font-Size="X-Small" Font-Bold="True" ForeColor="White"
BackColor=""></HeaderStyle>
<Columns>
<asp:TemplateColumn>
<HeaderTemplate>
<b>Results detail</b>
</HeaderTemplate>
<ItemTemplate>
<table border="0" Cellpadding="4" Cellspacing="0" Width="80%"
style="FONT-SIZE: 11px; FONT-FAMILY: Verdana, Arial, sans-serif">
<tr><td valign="top" unselectable="on">first_name</td>
<td><asp:TextBox id="txtFirstName" runat="server" Width="109px" Text='<%#
Container.DataItem("first_name")%>' /></td>
</tr>
<tr><td valign="top">last_name</td><td><asp:TextBox id="txtLastName"
runat="server" Width="109px" Text='<%# Container.DataItem("last_name")%>'
/></td></tr>
<tr><td valign="top">city</td><td><asp:TextBox id="txtCity" runat="server"
Width="109px" Text='<%# Container.DataItem("city")%>' /></td></tr>
</table>
</ItemTemplate>
</asp:TemplateColumn>
</Columns>
</asp:datagrid>
<br />
<asp:Button ID="updateBtn" Runat="server" Text="Save Changes"
onclick="saveRec" />
<asp:Button ID="cancelBtn" Runat="server" Text="Cancel"
onclick="cancel" />
<asp:Label TEXT="" ID="Label2" Runat="Server" />
</form>
</center>
</body>
</html>
