无法将类型'System.Collections.Generic.List <>'隐式转换为'System.Threading.Tasks.Task <>>

Question

I am getting an exception.

Cannot implicitly convert type 'System.Collections.Generic.List<IntegraPay.Domain.SObjects.Industry>' to 'System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<IntegraPay.Domain.SObjects.Industry>>'

Below is my property and method.

  private List<WebFormFieldContent> WebFormFields { get; set; } = 
       new List<WebFormFieldContent>();

  Task<IEnumerable<WebFormFieldContent>> IRegistrationRepository.GetWebFormFields()
        {
            return WebFormFields;
        }

Answer 1

This error typically happens when you are missing async in the method declaration.

When you put async in the signature, C# compiler adds "magic" to do the conversion from an object to a Task<T> returning that object.

However, in your situation async is unnecessary, because you return a task with a result that you already have:

return Task.FromResult<IEnumerable<WebFormFieldContent>>(
    WebFormFields
);

Answer 2

Your method return type is

Task<IEnumerable<WebFormFieldContent>> 

but the implementation returns a

List<WebFormFieldContent>. 

You can change it to

Task<List<WebFormFieldContent>> IRegistrationRepository.GetWebFormFields()
    {
        return Task.FromResult(WebFormFields);
    }

Or change the private variable to

IEnumerable<WebFormFieldContent> WebFormFields { get; set; } = 
   new List<WebFormFieldContent>();

type.

Or you can add an async key word to make it a synchronous call

async Task<IEnumerable<WebFormFieldContent>> IRegistrationRepository.GetWebFormFields()
    {
        return WebFormFields;
    }