Cannot implicitly convert type from Task

Question

I am trying to master async method syntax in  NET 4 5   I thought I had understood the examples exactly however no matter what the type of the async method is  ie Task lt T gt    I always get the same type of error error on the conversion back to T - which I understood was pretty much automatic   The following code produces the error      Cannot implicitly convert type  System Threading Tasks Task lt System Collections Generic List lt int gt  gt   to  System Collections Generic List lt int gt     public List lt int gt  TestGetMethod         return GetIdList       compiler error on this line     async Task lt List lt int gt  gt  GetIdList         using  HttpClient proxy   new HttpClient                  string response   await proxy GetStringAsync  www test com            List lt int gt  idList   JsonConvert DeserializeObject lt List lt int gt  gt             return idList            It fails if I explicitly cast the result as well   This   public List lt int gt  TestGetMethod         return  List lt int gt  GetIdList        compiler error on this line     somewhat predictably results in this error      Cannot convert type  System Threading Tasks Task lt System Collections Generic List lt int gt  gt   to  System Collections Generic List lt int gt     Any help greatly appreciated

User · Answer

The main issue with your example that you can't implicitly convert Task<T> return types to the base T type. You need to use the Task.Result property. Note that Task.Result will block async code, and should be used carefully.

Try this instead:

public List<int> TestGetMethod()  
{  
    return GetIdList().Result;  
}

User · Answer

You need to make TestGetMethod async too and attach await in front of GetIdList    will unwrap the task to List lt int gt   So if your helper function is returning Task make sure you have await as you are calling the function async too   public Task lt List lt int gt  gt  TestGetMethod         return GetIdList           async Task lt List lt int gt  gt  GetIdList         using  HttpClient proxy   new HttpClient                  string response   await proxy GetStringAsync  www test com            List lt int gt  idList   JsonConvert DeserializeObject lt List lt int gt  gt             return idList            Another option  public async void TestGetMethod List lt int gt  results        results   await GetIdList       await will unwrap the List lt int gt

User · Answer

Depending on what you re trying to do  you can either block with GetIdList   Result   generally a bad idea  but it s hard to tell the context  or use a test framework that supports async test methods and have the test method do var results   await GetIdList

[c#] Cannot implicitly convert type from Task<>

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