How to call web method in C# asynchronously?

Question

How to call web method in c# using async. I'm using like below

    public void SaveSuggestedItems(string emailbody, string OrderHeaderID)
    {
       try{
            ...
        }
        catch{
           ...
        }
    }

and in c# Im using like this

  public async Task<string> saveSuggestedItem()
    {
        OHDWebService OHDService = new OHDWebService();
        var saveSuggestedItem = OHDService.SaveSuggestedItems(eBody.Text, hfdOrderRecordID.Value);
        var suggestedItems = await saveSuggestedItem;
        return suggestedItems;
    }

but it is showing error like cannot assign void to an implicit typed local variable

You can't try to assing the return value fo a void method like `SaveSuggestedItems` to a variable. This has nothing to do with async/await. `async/await` won't make anything asynchronous automagically either, they make *awaiting* already asynchronous operations easier. Whatever is inside `SaveSuggestedItems` should use asynchronous methods itself — Panagiotis Kanavos, Jan 15 '19 at 10:14
BTW that's explained in ASP.NET tutorials. You'll probably save a lot of time if you follow a tutorial before starting a new project. Check for example [Tutorial: Create a web API with ASP.NET Core MVC](https://learn.microsoft.com/en-us/aspnet/core/tutorials/first-web-api?view=aspnetcore-2.2&tabs=visual-studio) — Panagiotis Kanavos, Jan 15 '19 at 10:16

John Wu · Answer 1 · 2019-01-15T10:26:54.343

4

You need to make the method async. Change this:

public void SaveSuggestedItems(string emailbody, string OrderHeaderID)

to this:

public async Task SaveSuggestedItems(string emailbody, string OrderHeaderID)

Now you can await it.

Note: You don't have to (and can't) actually return the Task explicitly. The compiler generates one for you.

Also, consider changing the name to SaveSuggestedItemsAsync().

Finally, make sure there's actually a need to make it async.

edited Jan 15 '19 at 10:26

answered Jan 15 '19 at 10:20

John Wu

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Thanq, actually "SaveSuggestedItems" method is reside in webservice its return type is void so we cant assign void to local variable, but i want to call that method in C# using asyn, so i created that function "saveSuggestedItem", I want make saveSuggestedItem as async but its giving error. – PK-1825 Jan 15 '19 at 11:36
Is `SaveSuggestedItems` code that was generated by adding a service reference? You need to tell Visual Studio to [generate async or task-based methods](https://stackoverflow.com/questions/13777710/how-to-use-visual-studio-generated-async-wcf-calls) as well (in the dialog that is shown when adding the reference). – John Wu Jan 15 '19 at 17:41

score 2 · Answer 2 · answered Jan 15 '19 at 10:15

Just replace:

var saveSuggestedItem = OHDService.SaveSuggestedItems(eBody.Text, hfdOrderRecordID.Value);

to standard calling:

OHDService.SaveSuggestedItems(eBody.Text, hfdOrderRecordID.Value);

Your problem appears because you try to assign void to some variable and your method does not return any type. It's not related to async calling.

How to call web method in C# asynchronously?

2 Answers2