What is the best way to determine a session variable is null or empty in C

Question

What is the best way to check for the existence of a session variable in ASP NET C      I like to use String IsNullOrEmpty   works for strings and wondered if there was a similar method for Session   Currently the only way I know of is    var session   if  Session  variable      null          session   Session  variable   ToString        else         session    set this        Session  variable     session

User · Answer

In my opinion  the easiest way to do this that is clear and easy to read is    String sVar    string  Session  SessionVariable       Default Value      It may not be the most efficient method  since it casts the default string value even in the case of the default  casting a string as string   but if you make it a standard coding practice  you find it works for all data types  and is easily readable   For example  a totally bogus example  but it shows the point     DateTime sDateVar    datetime  Session  DateValue       2010-01-01     Int NextYear   sDateVar Year   1   String Message    The Procrastinators Club will open it s doors Jan  1st                         string  Session  OpeningDate      NextYear     I like the Generics option  but it seems like overkill unless you expect to need this all over the place   The extensions method could be modified to specifically extend the Session object so that it has a  safe  get option like Session StringIfNull  SessionVar   and Session  SessionVar      myval    It breaks the simplicity of accessing the variable via Session  SessionVar    but it is clean code  and still allows validating if null or if string if you need it

User · Answer

Are you using  NET 3 5   Create an IsNull extension method   public static bool IsNull this object input        input    null   return true   return false     public void Main        object x   new object       if x IsNull               do your thing

User · Answer

To follow on from what others have said  I tend to have two layers   The core layer  This is within a DLL that is added to nearly all web app projects  In this I have a SessionVars class which does the grunt work for Session state getters setters  It contains code like the following   public class SessionVar       static HttpSessionState Session               get                       if  HttpContext Current    null                  throw new ApplicationException  No Http Context  No Session to Get                  return HttpContext Current Session                       public static T Get lt T gt  string key                if  Session key     null              return default T           else             return  T Session key              public static void Set lt T gt  string key  T value                Session key    value            Note the generics for getting any type   I then also add Getters Setters for specific types  especially string since I often prefer to work with string Empty rather than null for variables presented to Users   e g   public static string GetString string key        string s   Get lt string gt  key       return s    null   string Empty   s     public static void SetString string key  string value        Set lt string gt  key  value       And so on     I then create wrappers to abstract that away and bring it up to the application model  For example  if we have customer details   public class CustomerInfo       public string Name               get                       return SessionVar GetString  CustomerInfo Name                      set                       SessionVar SetString  CustomerInfo Name   value                       You get the idea right      NOTE  Just had a thought when adding a comment to the accepted answer  Always ensure objects are serializable when storing them in Session when using a state server  It can be all too easy to try and save an object using the generics when on  web farm and it go boom  I deploy on a web farm at work so added checks to my code in the core layer to see if the object is serializable  another benefit of encapsulating the Session Getters and Setters

User · Answer

in this way it can be checked whether such a key is available   if  Session Dictionary ContainsKey  Sessionkey     -- gt  return Bool

User · Answer

Are you using  NET 3 5   Create an IsNull extension method   public static bool IsNull this object input        input    null   return true   return false     public void Main        object x   new object       if x IsNull               do your thing

User · Answer

Typically I create SessionProxy with strongly typed properties for items in the session   The code that accesses these properties checks for nullity and does the casting to the proper type   The nice thing about this is that all of my session related items are kept in one place   I don t have to worry about using different keys in different parts of the code  and wondering why it doesn t work    And with dependency injection and mocking I can fully test it with unit tests   If follows DRY principles and also lets me define reasonable defaults   public class SessionProxy       private HttpSessionState session     use dependency injection for testability     public SessionProxy  HttpSessionState session                this session   session     might need to throw an exception here if session is null            public DateTime LastUpdate              get   return this session  LastUpdate      null                             DateTime this session  LastUpdate                               DateTime MinValue           set   this session  LastUpdate     value               public string UserLastName              get   return  string this session  UserLastName             set   this session  UserLastName     value

User · Answer

Are you using  NET 3 5   Create an IsNull extension method   public static bool IsNull this object input        input    null   return true   return false     public void Main        object x   new object       if x IsNull               do your thing

User · Answer

It may make things more elegant to wrap it in a property   string MySessionVar      get        return Session  MySessionVar      String Empty          set        Session  MySessionVar     value           then you can treat it as a string   if  String IsNullOrEmpty  MySessionVar             do something

User · Answer

I also like to wrap session variables in properties  The setters here are trivial  but I like to write the get methods so they have only one exit point  To do that I usually check for null and set it to a default value before returning the value of the session variable   Something like this   string Name      get              if Session  Name      Null             Session  Name      Default value          return  string Session  Name            set   Session  Name     value

User · Answer

Checking for nothing Null is the way to do it    Dealing with object types is not the way to go  Declare a strict type and try to cast the object to the correct type   And use cast hint or Convert    private const string SESSION VAR    myString    string sSession   if  Session SESSION VAR     null          sSession    string Session SESSION VAR       else         sSession    set this        Session SESSION VAR    sSession       Sorry for any syntax violations  I am a daily VB er

User · Answer

That is pretty much how you do it   However  there is a shorter syntax you can use   sSession    string Session  variable       set this     This is saying if the session variables is null  set sSession to  set this

User · Answer

The  as  notation in c  3 0 is very clean   Since all session variables are nullable objects  this lets you grab the value and put it into your own typed variable without worry of throwing an exception   Most objects can be handled this way   string mySessionVar   Session  mySessionVar   as string    My concept is that you should pull your Session variables into local variables and then handle them appropriately   Always assume your Session variables could be null and never cast them into a non-nullable type   If you need a non-nullable typed variable you can then use TryParse to get that   int mySessionInt  if   int TryParse mySessionVar  out mySessionInt          handle the case where your session variable did not parse into the expected type        e g  mySessionInt   0

User · Answer

If you know it s a string  you can use the String IsEmptyOrNull   function

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This method also does not assume that the object in the Session variable is a string  if  Session  MySessionVariable          ToString                More code for the Code God   So basically replaces the null variable with an empty string before converting it to a string since ToString is part of the Object class

User · Answer

Checking for nothing Null is the way to do it    Dealing with object types is not the way to go  Declare a strict type and try to cast the object to the correct type   And use cast hint or Convert    private const string SESSION VAR    myString    string sSession   if  Session SESSION VAR     null          sSession    string Session SESSION VAR       else         sSession    set this        Session SESSION VAR    sSession       Sorry for any syntax violations  I am a daily VB er

User · Answer

Typically I create SessionProxy with strongly typed properties for items in the session   The code that accesses these properties checks for nullity and does the casting to the proper type   The nice thing about this is that all of my session related items are kept in one place   I don t have to worry about using different keys in different parts of the code  and wondering why it doesn t work    And with dependency injection and mocking I can fully test it with unit tests   If follows DRY principles and also lets me define reasonable defaults   public class SessionProxy       private HttpSessionState session     use dependency injection for testability     public SessionProxy  HttpSessionState session                this session   session     might need to throw an exception here if session is null            public DateTime LastUpdate              get   return this session  LastUpdate      null                             DateTime this session  LastUpdate                               DateTime MinValue           set   this session  LastUpdate     value               public string UserLastName              get   return  string this session  UserLastName             set   this session  UserLastName     value

User · Answer

This method also does not assume that the object in the Session variable is a string  if  Session  MySessionVariable          ToString                More code for the Code God   So basically replaces the null variable with an empty string before converting it to a string since ToString is part of the Object class

User · Answer

Checking for nothing Null is the way to do it    Dealing with object types is not the way to go  Declare a strict type and try to cast the object to the correct type   And use cast hint or Convert    private const string SESSION VAR    myString    string sSession   if  Session SESSION VAR     null          sSession    string Session SESSION VAR       else         sSession    set this        Session SESSION VAR    sSession       Sorry for any syntax violations  I am a daily VB er

User · Answer

It may make things more elegant to wrap it in a property   string MySessionVar      get        return Session  MySessionVar      String Empty          set        Session  MySessionVar     value           then you can treat it as a string   if  String IsNullOrEmpty  MySessionVar             do something

User · Answer

If you know it s a string  you can use the String IsEmptyOrNull   function

User · Answer

To follow on from what others have said  I tend to have two layers   The core layer  This is within a DLL that is added to nearly all web app projects  In this I have a SessionVars class which does the grunt work for Session state getters setters  It contains code like the following   public class SessionVar       static HttpSessionState Session               get                       if  HttpContext Current    null                  throw new ApplicationException  No Http Context  No Session to Get                  return HttpContext Current Session                       public static T Get lt T gt  string key                if  Session key     null              return default T           else             return  T Session key              public static void Set lt T gt  string key  T value                Session key    value            Note the generics for getting any type   I then also add Getters Setters for specific types  especially string since I often prefer to work with string Empty rather than null for variables presented to Users   e g   public static string GetString string key        string s   Get lt string gt  key       return s    null   string Empty   s     public static void SetString string key  string value        Set lt string gt  key  value       And so on     I then create wrappers to abstract that away and bring it up to the application model  For example  if we have customer details   public class CustomerInfo       public string Name               get                       return SessionVar GetString  CustomerInfo Name                      set                       SessionVar SetString  CustomerInfo Name   value                       You get the idea right      NOTE  Just had a thought when adding a comment to the accepted answer  Always ensure objects are serializable when storing them in Session when using a state server  It can be all too easy to try and save an object using the generics when on  web farm and it go boom  I deploy on a web farm at work so added checks to my code in the core layer to see if the object is serializable  another benefit of encapsulating the Session Getters and Setters

User · Answer

To follow on from what others have said  I tend to have two layers   The core layer  This is within a DLL that is added to nearly all web app projects  In this I have a SessionVars class which does the grunt work for Session state getters setters  It contains code like the following   public class SessionVar       static HttpSessionState Session               get                       if  HttpContext Current    null                  throw new ApplicationException  No Http Context  No Session to Get                  return HttpContext Current Session                       public static T Get lt T gt  string key                if  Session key     null              return default T           else             return  T Session key              public static void Set lt T gt  string key  T value                Session key    value            Note the generics for getting any type   I then also add Getters Setters for specific types  especially string since I often prefer to work with string Empty rather than null for variables presented to Users   e g   public static string GetString string key        string s   Get lt string gt  key       return s    null   string Empty   s     public static void SetString string key  string value        Set lt string gt  key  value       And so on     I then create wrappers to abstract that away and bring it up to the application model  For example  if we have customer details   public class CustomerInfo       public string Name               get                       return SessionVar GetString  CustomerInfo Name                      set                       SessionVar SetString  CustomerInfo Name   value                       You get the idea right      NOTE  Just had a thought when adding a comment to the accepted answer  Always ensure objects are serializable when storing them in Session when using a state server  It can be all too easy to try and save an object using the generics when on  web farm and it go boom  I deploy on a web farm at work so added checks to my code in the core layer to see if the object is serializable  another benefit of encapsulating the Session Getters and Setters

User · Answer

Typically I create SessionProxy with strongly typed properties for items in the session   The code that accesses these properties checks for nullity and does the casting to the proper type   The nice thing about this is that all of my session related items are kept in one place   I don t have to worry about using different keys in different parts of the code  and wondering why it doesn t work    And with dependency injection and mocking I can fully test it with unit tests   If follows DRY principles and also lets me define reasonable defaults   public class SessionProxy       private HttpSessionState session     use dependency injection for testability     public SessionProxy  HttpSessionState session                this session   session     might need to throw an exception here if session is null            public DateTime LastUpdate              get   return this session  LastUpdate      null                             DateTime this session  LastUpdate                               DateTime MinValue           set   this session  LastUpdate     value               public string UserLastName              get   return  string this session  UserLastName             set   this session  UserLastName     value

User · Answer

That is pretty much how you do it   However  there is a shorter syntax you can use   sSession    string Session  variable       set this     This is saying if the session variables is null  set sSession to  set this

User · Answer

in this way it can be checked whether such a key is available   if  Session Dictionary ContainsKey  Sessionkey     -- gt  return Bool

User · Answer

The  as  notation in c  3 0 is very clean   Since all session variables are nullable objects  this lets you grab the value and put it into your own typed variable without worry of throwing an exception   Most objects can be handled this way   string mySessionVar   Session  mySessionVar   as string    My concept is that you should pull your Session variables into local variables and then handle them appropriately   Always assume your Session variables could be null and never cast them into a non-nullable type   If you need a non-nullable typed variable you can then use TryParse to get that   int mySessionInt  if   int TryParse mySessionVar  out mySessionInt          handle the case where your session variable did not parse into the expected type        e g  mySessionInt   0

User · Answer

That is pretty much how you do it   However  there is a shorter syntax you can use   sSession    string Session  variable       set this     This is saying if the session variables is null  set sSession to  set this

User · Answer

It may make things more elegant to wrap it in a property   string MySessionVar      get        return Session  MySessionVar      String Empty          set        Session  MySessionVar     value           then you can treat it as a string   if  String IsNullOrEmpty  MySessionVar             do something

User · Answer

I also like to wrap session variables in properties  The setters here are trivial  but I like to write the get methods so they have only one exit point  To do that I usually check for null and set it to a default value before returning the value of the session variable   Something like this   string Name      get              if Session  Name      Null             Session  Name      Default value          return  string Session  Name            set   Session  Name     value

User · Answer

The  as  notation in c  3 0 is very clean   Since all session variables are nullable objects  this lets you grab the value and put it into your own typed variable without worry of throwing an exception   Most objects can be handled this way   string mySessionVar   Session  mySessionVar   as string    My concept is that you should pull your Session variables into local variables and then handle them appropriately   Always assume your Session variables could be null and never cast them into a non-nullable type   If you need a non-nullable typed variable you can then use TryParse to get that   int mySessionInt  if   int TryParse mySessionVar  out mySessionInt          handle the case where your session variable did not parse into the expected type        e g  mySessionInt   0

User · Answer

In my opinion  the easiest way to do this that is clear and easy to read is    String sVar    string  Session  SessionVariable       Default Value      It may not be the most efficient method  since it casts the default string value even in the case of the default  casting a string as string   but if you make it a standard coding practice  you find it works for all data types  and is easily readable   For example  a totally bogus example  but it shows the point     DateTime sDateVar    datetime  Session  DateValue       2010-01-01     Int NextYear   sDateVar Year   1   String Message    The Procrastinators Club will open it s doors Jan  1st                         string  Session  OpeningDate      NextYear     I like the Generics option  but it seems like overkill unless you expect to need this all over the place   The extensions method could be modified to specifically extend the Session object so that it has a  safe  get option like Session StringIfNull  SessionVar   and Session  SessionVar      myval    It breaks the simplicity of accessing the variable via Session  SessionVar    but it is clean code  and still allows validating if null or if string if you need it

User · Answer

Checking for nothing Null is the way to do it    Dealing with object types is not the way to go  Declare a strict type and try to cast the object to the correct type   And use cast hint or Convert    private const string SESSION VAR    myString    string sSession   if  Session SESSION VAR     null          sSession    string Session SESSION VAR       else         sSession    set this        Session SESSION VAR    sSession       Sorry for any syntax violations  I am a daily VB er

User · Answer

Typically I create SessionProxy with strongly typed properties for items in the session   The code that accesses these properties checks for nullity and does the casting to the proper type   The nice thing about this is that all of my session related items are kept in one place   I don t have to worry about using different keys in different parts of the code  and wondering why it doesn t work    And with dependency injection and mocking I can fully test it with unit tests   If follows DRY principles and also lets me define reasonable defaults   public class SessionProxy       private HttpSessionState session     use dependency injection for testability     public SessionProxy  HttpSessionState session                this session   session     might need to throw an exception here if session is null            public DateTime LastUpdate              get   return this session  LastUpdate      null                             DateTime this session  LastUpdate                               DateTime MinValue           set   this session  LastUpdate     value               public string UserLastName              get   return  string this session  UserLastName             set   this session  UserLastName     value

User · Answer

To follow on from what others have said  I tend to have two layers   The core layer  This is within a DLL that is added to nearly all web app projects  In this I have a SessionVars class which does the grunt work for Session state getters setters  It contains code like the following   public class SessionVar       static HttpSessionState Session               get                       if  HttpContext Current    null                  throw new ApplicationException  No Http Context  No Session to Get                  return HttpContext Current Session                       public static T Get lt T gt  string key                if  Session key     null              return default T           else             return  T Session key              public static void Set lt T gt  string key  T value                Session key    value            Note the generics for getting any type   I then also add Getters Setters for specific types  especially string since I often prefer to work with string Empty rather than null for variables presented to Users   e g   public static string GetString string key        string s   Get lt string gt  key       return s    null   string Empty   s     public static void SetString string key  string value        Set lt string gt  key  value       And so on     I then create wrappers to abstract that away and bring it up to the application model  For example  if we have customer details   public class CustomerInfo       public string Name               get                       return SessionVar GetString  CustomerInfo Name                      set                       SessionVar SetString  CustomerInfo Name   value                       You get the idea right      NOTE  Just had a thought when adding a comment to the accepted answer  Always ensure objects are serializable when storing them in Session when using a state server  It can be all too easy to try and save an object using the generics when on  web farm and it go boom  I deploy on a web farm at work so added checks to my code in the core layer to see if the object is serializable  another benefit of encapsulating the Session Getters and Setters

User · Answer

If you know it s a string  you can use the String IsEmptyOrNull   function

User · Answer

If you know it s a string  you can use the String IsEmptyOrNull   function

User · Answer

It may make things more elegant to wrap it in a property   string MySessionVar      get        return Session  MySessionVar      String Empty          set        Session  MySessionVar     value           then you can treat it as a string   if  String IsNullOrEmpty  MySessionVar             do something

User · Answer

I also like to wrap session variables in properties  The setters here are trivial  but I like to write the get methods so they have only one exit point  To do that I usually check for null and set it to a default value before returning the value of the session variable   Something like this   string Name      get              if Session  Name      Null             Session  Name      Default value          return  string Session  Name            set   Session  Name     value

User · Answer

Are you using  NET 3 5   Create an IsNull extension method   public static bool IsNull this object input        input    null   return true   return false     public void Main        object x   new object       if x IsNull               do your thing

User · Answer

I also like to wrap session variables in properties  The setters here are trivial  but I like to write the get methods so they have only one exit point  To do that I usually check for null and set it to a default value before returning the value of the session variable   Something like this   string Name      get              if Session  Name      Null             Session  Name      Default value          return  string Session  Name            set   Session  Name     value

User · Answer

The  as  notation in c  3 0 is very clean   Since all session variables are nullable objects  this lets you grab the value and put it into your own typed variable without worry of throwing an exception   Most objects can be handled this way   string mySessionVar   Session  mySessionVar   as string    My concept is that you should pull your Session variables into local variables and then handle them appropriately   Always assume your Session variables could be null and never cast them into a non-nullable type   If you need a non-nullable typed variable you can then use TryParse to get that   int mySessionInt  if   int TryParse mySessionVar  out mySessionInt          handle the case where your session variable did not parse into the expected type        e g  mySessionInt   0

User · Answer

That is pretty much how you do it   However  there is a shorter syntax you can use   sSession    string Session  variable       set this     This is saying if the session variables is null  set sSession to  set this

[c#] What is the best way to determine a session variable is null or empty in C#?

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