TempData keep vs peek

Question

What is the difference between keep   and peek     MSDN says    keep    marks the specified key in the dictionary for retention  peek    returns an object that contains the element that is associated with the specified key  without marking the key for deletion    I can t get really what the difference is  don t they both keep a value for another request

User · Accepted Answer

When an object in a TempDataDictionary is read  it will be marked for deletion at the end of that request   That means if you put something on TempData like  TempData  value      someValueForNextRequest     And on another request you access it  the value will be there but as soon as you read it  the value will be marked for deletion     second request  read value and is marked for deletion object value   TempData  value       third request  value is not there as it was deleted at the end of the second request TempData  value      null   The Peek and Keep methods allow you to read the value without marking it for deletion  Say we get back to the first request where the value was saved to TempData   With Peek you get the value without marking it for deletion with a single call  see msdn     second request  PEEK value so it is not deleted at the end of the request object value   TempData Peek  value       third request  read value and mark it for deletion object value   TempData  value      With Keep you specify a key that was marked for deletion that you want to keep  Retrieving the object and later on saving it from deletion are 2 different calls  See msdn    second request  get value marking it from deletion object value   TempData  value      later on decide to keep it TempData Keep  value       third request  read value and mark it for deletion object value   TempData  value      You can use Peek when you always want to retain the value for another request  Use Keep when retaining the value depends on additional logic   You have 2 good questions about how TempData works here and here  Hope it helps

User · Answer

don t they both keep a value for another request    Yes they do  but when the first one is void  the second one returns and object   public void Keep string key         retainedKeys Add key      just adds the key to the collection for retention    public object Peek string key        object value       data TryGetValue key  out value       return value     returns an object without marking it for deletion

User · Answer

Just finished understanding Peek and Keep and had same confusion initially  The confusion arises becauses TempData behaves differently under different condition  You can watch this video which explains the Keep and Peek with demonstration https   www facebook com video php v 689393794478113   Tempdata helps to preserve values for a single request and CAN ALSO preserve values for the next request depending on 4 conditions       If we understand these 4 points you would see more clarity Below is a diagram with all 4 conditions  read the third and fourth point which talks about Peek and Keep     Condition 1  Not read  - If you set a    TempData    inside your action and if you do not read it in your view then    TempData    will be persisted for the next request   Condition 2    Normal Read   - If you read the    TempData    normally like the below code it will not persist for the next request   string str   TempData  MyData      Even if you are displaying it   s a normal read like the code below    TempData  MyData      Condition 3  Read and Keep   - If you read the    TempData    and call the    Keep    method it will be persisted    TempData  MyData    TempData Keep  MyData      Condition 4   Peek and Read   - If you read    TempData    by using the    Peek    method it will persist for the next request   string str   TempData Peek  Td   ToString      Reference  - http   www codeproject com Articles 818493 MVC-Tempdata-Peek-and-Keep-confusion

User · Answer

TempData is also a dictionary object that stays for the time of an  HTTP Request  So  TempData can be used to maintain data between one  controller action to the other controller action   TempData is used to check the null values each time  TempData contain  two method keep   and peek   for maintain data state from one  controller action to others   When  TempDataDictionary  object is read  At the end of request marks  as deletion to current read object   The keep   and peek   method is used to read the data without deletion  the current read object   You can use Peek   when you always want to hold prevent the value for  another request  You can use Keep   when prevent hold the value  depends on additional logic   Overloading in TempData Peek    amp  TempData Keep   as given below   TempData Keep   have 2 overloaded methods    void keep     That menace all the data not deleted on current request completion  void keep string key    persist the specific item in TempData with help of name    TempData Peek   no overloaded methods    object peek string key    return an object that contain items with specific key without making key for deletion    Example for return type of TempData Keep    amp  TempData Peek   methods as given below      public void Keep string key           retainedKeys Add key          public object Peek string key          object value   values        return value

User · Answer

Keep   method marks the specified key in the dictionary for retention  You can use Keep   when prevent hold the value depends on additional logic   when you read TempData  one   s and want to hold for another request then use keep method  so TempData can available for next request as above example

[asp.net-mvc] TempData keep() vs peek()

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