I am overriding a method in a base class library. However, inside my overridden implementation I am using the new HttpClient which is all based on async methods. I therefore have to mark my method as async, which means that I need to change the return parameter of the method from string to Task. The compiler however gives an error: "The return type must be 'string' to match overridden member ...."
public class BaseClass
{
public virtual string GetName()
{
...
}
}
public class MyClass : BaseClass
{
public override async Task<string> GetName()
{
HttpClient httpClient = new HttpClient();
var response = await httpClient.GetAsync("");
if (response.IsSuccessStatusCode)
{
var responseContent = response.Content;
return await responseContent.ReadAsStringAsync();
}
return null;
}
}
Of course the obvious solution would be to change the return type of GetName() in BaseClass to Task<string>, but I have no control over BaseClass as it is an external library;
My current solution is to use the HttpClient classes in a synchronous fashion, i.e. change MyClass as follows:
public class MyClass : BaseClass
{
public override string GetName()
{
HttpClient httpClient = new HttpClient();
var response = httpClient.GetAsync("");
if (response.Result.IsSuccessStatusCode)
{
var responseContent = response.Result.Content;
return responseContent.ReadAsStringAsync()
.Result;
}
return null;
}
}
Is there any other way to do this?
Unfortunately there isn't a good solution here. There is no way to override
a non-async method with an async one. I think your best bet is to have an async
non-override method and call into that from the non-async one:
public class MyClass : BaseClass
{
public override string GetName()
{
return GetNameAsync().Value;
}
public async Task<string> GetNameAsync()
{
...
}
}
Note that this can cause problems though. If the original code didn't expect for any async
code to be executing introducing this pattern could break expectations. I would avoid it if possible.
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