The server-side asp program can accept parameters from the form on the html page, so how does it implement IE address parameter judgment? When the address bar does not have the parameter "id":
Copy the code code as follows:
Request.QueryString[ID] == null
Convert.ToString(Request.QueryString[ID]) == null
Note that this will go wrong:
Request.QueryString[ID].ToString();
When the address bar has the parameter "id" but no value is assigned:
Copy the code code as follows:
Request.QueryString[ID] ==
Request.QueryString[ID] == String.Empty
Convert.ToString(Request.QueryString[ID]) ==
Convert.ToString(Request.QueryString[ID]) == String.Empty
When judging two conditions at the same time:
Copy the code code as follows:
if ( + Request.QueryString[ID] == ) {...}
if (( + Request.QueryString[ID]).Length == 0) {...}