How to Select a record using Listbox and edit/update it’s fields using textboxes

<TABLE class='cdb-AltRow2' id='Table1' style='Z-INDEX: 101; LEFT: 189px; POSITION: absolute; TOP: 20px' cellSpacing='1' cellPadding='1' width='300' border='0'>
	<TR>
	<TD>ProductID</TD>
	<TD><asp:textbox id='txtProductId' runat='server' Enabled='False'></asp:textbox></TD>
	</TR>
	<TR>
	<TD>Quantity per unit</TD>
	<TD><asp:textbox id='txtQuantity' runat='server'></asp:textbox></TD>
	</TR>
	<TR>
	<TD>UnitPrice</TD>
	<TD><asp:textbox id='txtUnitPrice' runat='server'></asp:textbox></TD>
	</TR>
	<TR>
	<TD></TD>
	<TD><asp:button id='btnUpdate' runat='server' Text='Update'></asp:button></TD>
	</TR>
	<TR>
	<TD></TD>
	<TD><asp:label id='lblError' runat='server' Visible='False'></asp:label></TD>
	</TR>
	</TABLE>
<asp:listbox id='ListBox1' style='Z-INDEX: 102; LEFT: 8px; POSITION: absolute; TOP: 12px' runat='server' AutoPostBack='True'></asp:listbox>

VB.NET

Dim productid As String
Dim strSQL As String
Dim strConn As String
Dim dr, dr1 As SqlDataReader
Dim mycn As SqlConnection
Dim mycmd As SqlCommand

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
	strConn = 'server=localhost;uid=sa;database=northwind;pwd=;'
	lblError.Visible = False
	’ Put user code to initialize the page here
	If Not Page.IsPostBack Then
	            mycn = New SqlConnection(strConn)
	            strSQL = 'Select * from Products'
	            mycmd = New SqlCommand(strSQL, mycn)
	            mycn.Open()
	            dr = mycmd.ExecuteReader(CommandBehavior.CloseConnection)
	            ListBox1.DataSource = dr
	            ListBox1.DataTextField = 'ProductID'
	            ListBox1.DataValueField = 'ProductID'
	            ListBox1.DataBind()
	End If
End Sub ’Page_Load

Private Sub btnUpdate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnUpdate.Click
        Try
	lblError.Visible = False
	Dim updateCmd As String = 'UPDATE Products SET QuantityPerUnit = @QuantityPerUnit ,' + 'UnitPrice = @UnitPrice  where ProductId=@ProductId'
	Dim cn As New SqlConnection(strConn)
	Dim myCommand As New SqlCommand(updateCmd, cn)
	myCommand.Parameters.Add(New SqlParameter('@QuantityPerUnit', txtQuantity.Text))
	myCommand.Parameters.Add(New SqlParameter('@UnitPrice', Convert.ToDouble(txtUnitPrice.Text)))
	myCommand.Parameters.Add(New SqlParameter('@ProductId', Convert.ToInt16(txtProductId.Text)))
	cn.Open()
	myCommand.ExecuteNonQuery()
	lblError.Visible = True
	lblError.Text = 'Record Updated successfully'
        Catch ex As Exception
        	lblError.Visible = True
	lblError.Text = ex.Message
        End Try
End Sub ’btnUpdate_Click


Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
	productid = ListBox1.SelectedItem.Value
	txtProductId.Text = productid.ToString()
	strSQL = 'Select * from Products where productid =' + productid
	mycn = New SqlConnection(strConn)
	mycmd = New SqlCommand(strSQL, mycn)
	mycn.Open()
	dr1 = mycmd.ExecuteReader(CommandBehavior.CloseConnection)
	If dr1.Read() Then
	            txtProductId.Text = dr1('ProductId').ToString()
	            txtQuantity.Text = dr1('QuantityPerUnit').ToString()
	            txtUnitPrice.Text = dr1('UnitPrice').ToString()
	Else
	            Response.Write('No data found')
	End If
End Sub ’ListBox1_SelectedIndexChanged 

C#

string productid;
string strSQL;
string strConn;
SqlDataReader dr,dr1;
SqlConnection mycn;
SqlCommand mycmd;

private void Page_Load(object sender, System.EventArgs e)
{
	strConn ='server=localhost;uid=sa;database=northwind;pwd=;';
	lblError.Visible =false;
	// Put user code to initialize the page here
	if (!Page.IsPostBack )
	{
		mycn = new SqlConnection(strConn);
		strSQL ='Select * from Products';
		mycmd = new SqlCommand  (strSQL, mycn);
		mycn.Open ();
		dr=mycmd.ExecuteReader(CommandBehavior.CloseConnection ); 
		ListBox1.DataSource = dr;
		ListBox1.DataTextField ='ProductID';
		ListBox1.DataValueField ='ProductID';
		ListBox1.DataBind ();
	}
}

private void btnUpdate_Click(object sender, System.EventArgs e)
{
	try
	{
		lblError.Visible =false;

		string updateCmd = 'UPDATE Products SET QuantityPerUnit = @QuantityPerUnit ,'
				+ 'UnitPrice = @UnitPrice  where ProductId=@ProductId';
				 
		SqlConnection cn = new SqlConnection (strConn);
		SqlCommand myCommand = new SqlCommand(updateCmd, cn);
		myCommand.Parameters.Add(new SqlParameter('@QuantityPerUnit', txtQuantity.Text   ));
		myCommand.Parameters.Add(new SqlParameter('@UnitPrice', Convert.ToDouble( txtUnitPrice.Text  )));
		myCommand.Parameters.Add(new SqlParameter('@ProductId', Convert.ToInt16 ( txtProductId.Text)));
		cn.Open ();
		myCommand.ExecuteNonQuery ();
		lblError.Visible =true;
		lblError.Text ='Record Updated successfully';
	}
	catch(Exception ex)
	{
		lblError.Visible =true;
		lblError.Text =(ex.Message );
	}
}

private void ListBox1_SelectedIndexChanged(object sender, System.EventArgs e)
{
	productid = ListBox1.SelectedItem.Value  ;
	txtProductId.Text =productid.ToString ();
	strSQL = 'Select * from Products where productid =' + productid ;
	mycn = new SqlConnection(strConn);
	mycmd = new SqlCommand  (strSQL, mycn);
	mycn.Open ();
	dr1=mycmd.ExecuteReader(CommandBehavior.CloseConnection ); 
	if(dr1.Read() )
	{
		txtProductId.Text = dr1['ProductId'].ToString ();
		txtQuantity.Text = dr1['QuantityPerUnit'].ToString ();
		txtUnitPrice.Text = dr1['UnitPrice'].ToString ();
	}
	else
	{
		Response.Write ('No data found');
	}
}