I had written a simple example here.
Below code has simple example on it:
<%
@.PageLanguage="VB" %><%
@.ImportNamespace="System.Data" %><%
@.ImportNamespace="System.Data.SqlClient" %><scriptrunat="server">
ProtectedSub btnCheckData_Click(ByVal senderAsObject,ByVal eAs System.EventArgs)TryDim HasdataAsStringDim myConnectionAsNew SqlConnection("server=server\sqlserver;database=db;User Id=uid;Password=swd;")Dim myCommandAsNew SqlCommand( _"Select 'X' from preview Where facility='" & TextBox1.Text &"'", myConnection)
myCommand.Connection.Open()
Hasdata = myCommand.ExecuteScalar()
myCommand.Connection.Close()
myCommand.Connection.Dispose()
If Hasdata ="X"Then' Do if data exist process here
Response.Write("Data exit")
Else
' Do if data not exist process here
Response.Write("Data not exist")
EndIfCatch exAs Exception
Response.Write(
"Error:" & ex.Message)ExitSubEndTryEndSub</
script><
htmlxmlns="http://www.w3.org/1999/xhtml"><
headrunat="server"><title>Untitled Page</title></
head><
body><formid="form1"runat="server"><div> <asp:TextBoxID="TextBox1"runat="server"></asp:TextBox><br/><br/><asp:ButtonID="btnCheckData"runat="server"OnClick="btnCheckData_Click"Text="CheckData"/></div></form></
body></
html>I have used executescalar and checked data is there or not in above example. If you see select, in that I am taking input from textbox for where clause, I am checking if that value is in DB or not, if not we won't get any data, but if the value is there, then select returns 'X'. So by basing on that I am checking the If condition as below.
If Hasdata ="X"Then
' Do if data exist process here
Response.Write("Data exit")
Else
' Do if data not exist process here
Response.Write("Data not exist")
EndIf
So as you asked if data is there you can keep it in True condition or if not there then you can keep in false condition.
Hope it helps!
|||Thanks for the help. When I run the code, I get an error telling me I need to cast to string (I'm using c#). And when I fix that line to this: rescheck = (string)cmd.ExecuteScalar(); It says: Invalid column name 'Owner'Any ideas on how to fix this?
Thanks|||
Here is C# code:
<%@. Page Language="C#" %>
<%@. Import Namespace="System.Data" %>
<%@. Import Namespace="System.Data.SqlClient" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void btnCheckData_Click(object sender, EventArgs e)
{
try
{
String Hasdata;
SqlConnection myConnection = new SqlConnection(@."server=Sreebrain\SreeSQL;database=SriTest;User Id=sa;Password=srikog1!;");
SqlCommand myCommand = new SqlCommand( "Select 'X' from preview Where facility='" + TextBox1.Text + "'", myConnection);
myCommand.Connection.Open();
Hasdata = (string)myCommand.ExecuteScalar();
myCommand.Connection.Close();
myCommand.Connection.Dispose();
if (Hasdata == "X")
{
// Do if data exist process here
Response.Write("Data exit");
}
else
{
// Do if data not exist process here
Response.Write("Data not exist");
}
}
catch (Exception ex)
{
Response.Write("Error:" + ex.Message);
}
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<br />
<br />
<asp:Button ID="btnCheckData" runat="server" OnClick="btnCheckData_Click" Text="CheckData" /></div>
</form>
</body>
</html>
Ok, You got invalid column means, In your select statement you might given a column name as owner, that field could not be in your Table.
Ex: Select 'X' from preview
Instead of column name give 'X' there so that you can check for 'X' when you got the result back.
Also make sure in your where clause you given the disered field as you wanted.
If you still get error after you do these changes, please post the code, so that I can invistigate the problem.
Hope this time it will make you clear!
|||Thanks for all the help. You were right on the money. Everything's fixed :)|||I have 2 labels with visibility set to FALSE, I want to display 1 label when the entry exists and the other 1 when the entry does not exist in my DB
your code looks like it should work, yet I am getting some exceptional error
here the error
Object reference not set to an instance of an object.
Description:An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.Exception Details:System.NullReferenceException: Object reference not set to an instance of an object.
Source Error:
Line 61: If Hasdata = "X" Then
Line 62: Label12.Visible = True
Line 63: Else
Line 64: Label9.Visible = True
Line 65: End If
Source File:D:\Visual Studio 2005\Projects\WebApplication11\WebApplication11\admin\Createu.aspx.vb Line:63
Stack Trace:
[NullReferenceException: Object reference not set to an instance of an object.]
WebApplication11.Createu.TextBox1_TextChanged(Object sender, EventArgs e) in D:\Visual Studio 2005\Projects\WebApplication11\WebApplication11\admin\Createu.aspx.vb:63
System.Web.UI.WebControls.TextBox.OnTextChanged(EventArgs e) +105
System.Web.UI.WebControls.TextBox.RaisePostDataChangedEvent() +134
System.Web.UI.WebControls.TextBox.System.Web.UI.IPostBackDataHandler.RaisePostDataChangedEvent() +7
System.Web.UI.Page.RaiseChangedEvents() +137
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4778
Version Information: Microsoft .NET Framework Version:2.0.50727.832; ASP.NET Version:2.0.50727.832
and heres the code
Protected Sub TextBox1_TextChanged(ByVal senderAs System.Object,ByVal eAs System.EventArgs)Handles TextBox1.TextChangedTry Dim HasdataAs String Dim myConnectionAs New SqlConnection("Server=localhost;UID=SA;PWD=****;database=knowledge")Dim myCommandAs New SqlCommand("Select'X' from usr Where Uid='" & TextBox1.Text & "'", myConnection) myCommand.Connection.Open() Hasdata = myCommand.ExecuteScalar() myCommand.Connection.Close() myCommand.Connection.Dispose() If Hasdata = "X" Then Label12.Text = True Else Label9.Visible = True End If Catch ex As Exception Response.Write("Error:" & ex.Message)Exit Sub End Try End Sub
No comments:
Post a Comment