Many things can fail:

• e.CommandArgument may not be an integer
• e.CommandSource may not be of Control type
• the NamingContainer may not be of GridViewRow type
• myRow can be null, at least when the code is ran
• the "Label5" control may not be found, or may not be of Label type, when the code is ran
• the "Literal3" control may not be found (null ref) or may not be of Literal type, when the code is ran ...