C nullable string error

Question

private string  typeOfContract     get   return  string  ViewState  typeOfContract        set   ViewState  typeOfContract     value        Later in the code I use it like this   typeOfContract   Request QueryString  type      I am getting the following error at the declaration of typeOfContract line stating      The type  string  must be a non-nullable value type in order to use   it as parameter  T  in the generic type or method    System Nullable lt T     Any ideas  Basically  I want to make sure that  type  exists in the QueryString before performing an action

User · Accepted Answer

System String is a reference type and already  nullable    Nullable lt T  and the   suffix are for value types such as Int32  Double  DateTime  etc

User · Answer

String is a reference type  so you don t need to  and cannot  use Nullable lt T gt  here  Just declare typeOfContract as string and simply check for null after getting it from the query string  Or use String IsNullOrEmpty if you want to handle empty string values the same as null

User · Answer

You are making it complicated  string is already nullable  You don t need to make it more nullable  Take out the   on the property type

User · Answer

You are making it complicated  string is already nullable  You don t need to make it more nullable  Take out the   on the property type

User · Answer

string cannot be the parameter to Nullable because string is not a value type  String is a reference type    string s   null     is a very valid statement and there is not need to make it nullable   private string typeOfContract             get   return ViewState  typeOfContract   as string          set   ViewState  typeOfContract     value            should work because of the as keyword

User · Answer

string cannot be the parameter to Nullable because string is not a value type  String is a reference type    string s   null     is a very valid statement and there is not need to make it nullable   private string typeOfContract             get   return ViewState  typeOfContract   as string          set   ViewState  typeOfContract     value            should work because of the as keyword

User · Answer

For nullable  use   with all of the C  primitives  except for string   The following page gives a list of the C  primitives  http   msdn microsoft com en-us library aa711900 v vs 71  aspx

User · Answer

String is a reference type  so you don t need to  and cannot  use Nullable lt T gt  here  Just declare typeOfContract as string and simply check for null after getting it from the query string  Or use String IsNullOrEmpty if you want to handle empty string values the same as null

User · Answer

Please note that in upcoming version of C  which is 8  the answers are not true    All the reference types are non-nullable by default and you can actually do the following    public string  MyNullableString   this MyNullableString   null    Valid   However    public string MyNonNullableString   this MyNonNullableString   null    Not Valid and you ll receive compiler warning     The important thing here is to show the intent of your code   If the  intent  is that the reference type can be null  then mark it so otherwise assigning null value to non-nullable would result in compiler warning    More info  To the moderator who is deleting all the answers  don t do it  I strongly believe this answer adds value and deleting would simply keep someone from knowing what is right at the time  Since you have deleted all the answers  I m re-posting answer here  The link that was sent regarding  duplicates  is simply an opening of some people and I do not think it is an official recommendation

User · Answer

You are making it complicated  string is already nullable  You don t need to make it more nullable  Take out the   on the property type

User · Answer

string cannot be the parameter to Nullable because string is not a value type  String is a reference type    string s   null     is a very valid statement and there is not need to make it nullable   private string typeOfContract             get   return ViewState  typeOfContract   as string          set   ViewState  typeOfContract     value            should work because of the as keyword

User · Answer

String is a reference type  so you don t need to  and cannot  use Nullable lt T gt  here  Just declare typeOfContract as string and simply check for null after getting it from the query string  Or use String IsNullOrEmpty if you want to handle empty string values the same as null

User · Answer

Please note that in upcoming version of C  which is 8  the answers are not true    All the reference types are non-nullable by default and you can actually do the following    public string  MyNullableString   this MyNullableString   null    Valid   However    public string MyNonNullableString   this MyNonNullableString   null    Not Valid and you ll receive compiler warning     The important thing here is to show the intent of your code   If the  intent  is that the reference type can be null  then mark it so otherwise assigning null value to non-nullable would result in compiler warning    More info  To the moderator who is deleting all the answers  don t do it  I strongly believe this answer adds value and deleting would simply keep someone from knowing what is right at the time  Since you have deleted all the answers  I m re-posting answer here  The link that was sent regarding  duplicates  is simply an opening of some people and I do not think it is an official recommendation

User · Answer

You are making it complicated  string is already nullable  You don t need to make it more nullable  Take out the   on the property type

User · Answer

For nullable  use   with all of the C  primitives  except for string   The following page gives a list of the C  primitives  http   msdn microsoft com en-us library aa711900 v vs 71  aspx

User · Answer

string cannot be the parameter to Nullable because string is not a value type  String is a reference type    string s   null     is a very valid statement and there is not need to make it nullable   private string typeOfContract             get   return ViewState  typeOfContract   as string          set   ViewState  typeOfContract     value            should work because of the as keyword

User · Answer

String is a reference type  so you don t need to  and cannot  use Nullable lt T gt  here  Just declare typeOfContract as string and simply check for null after getting it from the query string  Or use String IsNullOrEmpty if you want to handle empty string values the same as null

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