How to check that Request QueryString has a specific value or not in ASP NET

Question

I have an error aspx page   If a user comes to that page then it will fetch the error path in page load   method URL using Request QueryString  aspxerrorpath   and it works fine   But if a user directly accesses that page the it will generate an exception because aspxerrorpath is not there   How can I check that aspxerrorpath is there or not

User · Answer

Check for the value of the parameter       NET  lt  4 0 if  string IsNullOrEmpty Request QueryString  aspxerrorpath           not there         NET  gt   4 0 if  string IsNullOrWhiteSpace Request QueryString  aspxerrorpath           not there      If it does not exist  the value will be null  if it does exist  but has no value set it will be an empty string   I believe the above will suit your needs better than just a test for null  as an empty string is just as bad for your specific situation

User · Answer

string IsNullOrEmpty Request QueryString  aspxerrorpath      true - gt  there is no value   Will return if there is a value

User · Answer

To check for an empty QueryString you should use Request QueryString HasKeys property   To check if the key is present  Request QueryString AllKeys Contains    Then you can get ist s Value and do any other check you want  such as isNullOrEmpty  etc

User · Answer

What about a more direct approach   if  Request QueryString AllKeys Contains  mykey

User · Answer

You can just check for null   if Request QueryString  aspxerrorpath    null         your code that depends on aspxerrorpath here

User · Answer

think the check you re looking for is this   if Request QueryString  query      null     It returns null because in that query string it has no value for that key

User · Answer

To resolve your problem  write the following line on your page s Page Load method   if  String IsNullOrEmpty Request QueryString  aspxerrorpath     return     Net 4 0 provides more closer look to null  empty or whitespace strings  use it as shown in the following line   if string IsNullOrWhiteSpace Request QueryString  aspxerrorpath     return    This will not run your next statements  your business logics  if query string does not have aspxerrorpath

User · Answer

You can also try   if   Request QueryString AllKeys Contains  aspxerrorpath       return

[c#] How to check that Request.QueryString has a specific value or not in ASP.NET?

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