Database

Select * from Table 
where ( (@ID = NULL) or (ID = @ID) )

Select * from Table 
where ( (@ID IS NULL) or (ID = @ID) )

Select * from Table 
where ( (ID IS NULL) or (ID = @ID) )

public void OnSavePassword(object sender, System.EventArgs e)
{
	if(EditPassword.Text == "")
	{
		ERROR.Text = "Du har inte skrivit in ett lösenord!";
		return;
	}

	string connectString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("/mp219.mdb");
	OleDbConnection connection = new OleDbConnection(connectString);
	
	try
	{
		StringBuilder commandString = new StringBuilder();
		commandString.Append("UPDATE Login SET Password='");
		commandString.Append(EditPassword.Text);
		commandString.Append("' WHERE User='");
		commandString.Append(Context.User.Identity.Name);
		commandString.Append("'");
		
		Response.Write(commandString.ToString());
		
		OleDbCommand cmd = new OleDbCommand(commandString.ToString(), connection);
		
		connection.Open();
		
		cmd.ExecuteNonQuery();
	}
	catch(Exception ex)
	{
		Response.Write("<br><br>");
		Response.Write(ex.ToString());
		ERROR.Text = "Ett undantag kastades, försök igen!";
		return;
	}
	finally
	{
		connection.Close();
	}
	
	SUCCESS.Text = "Lösenordet är ändrat!";
}