How to get exact exception issue

Question

I am using below code in My Error page , its working fine but want to get the exact issue of exception ,to resolve it , How can I do this for the same..

 

What I have tried:

if (ex != null)
{
StringBuilder lasterror = new StringBuilder();
if (ex.Message != null)
{
lasterror.AppendLine("Message:");
lasterror.AppendLine(ex.Message);
lasterror.AppendLine();
}
if (ex.InnerException != null)
{
lasterror.AppendLine("
InnerException:");
lasterror.AppendLine(ex.InnerException.ToString());
lasterror.AppendLine();
}

if (ex.Source != null)
{
lasterror.AppendLine("
Source:");
lasterror.AppendLine(ex.Source);
lasterror.AppendLine();
}

if (ex.StackTrace != null)
{
lasterror.AppendLine("
StackTrace:");
lasterror.AppendLine(ex.StackTrace);
lasterror.AppendLine();
}

lblException.Text = lasterror.ToString();
}