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":
Here is a quote:
Request.QueryString["ID"] == null
Convert.ToString(Request.QueryString["ID"]) == null
Note that this will cause an error:
Request.QueryString["ID"].ToString();
When the address bar has the parameter "id" but no value is assigned:
Here is a quote:
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:
The following is a quotation fragment:
if ("" + Request.QueryString["ID"] == "") {...}
if (("" + Request.QueryString["ID"]).Length == 0) {...}