Hi,
You are trying to convert string value to Int32, that is not quite possible.
For example see this snipper
string temp = string.Empty;
temp = temp + " Test string ";
int val = Convert.ToInt32(temp);
In your code, problematic line is
this.Image_sqlcmd.Parameters[Convert.ToInt32("@SID")].Value =Convert.ToInt32(this.txtsid.Text);
So you have to decide should I need to convert it to Int or not....
Your call.
Hope this helps you a bit.
Regards,
RK