async not working with Visual Studio 2010 and .NET 4.0?

Question

I have an below C# Code,It works fine in Visual studio 2017 with .Net Framework 4.0,But when I run the same source code in visual studio 2010 with .net Framework then its not working and its shows an compiled error message near async and wait .Please advise the alternate solution to do this.

Source Code :-

static string url = "https://einvoicing.internal.cleartax.co/v2/eInvoice/download?irns=7b46fb61d6e0883bdfdfb997ca25c4b5629d3062241532f6e8e6fcdfc0a95c9a";
static HttpClient client = new HttpClient(); 
static async Task DownloadCurrentAsync(string StrInvoiceNo)
        {

            client.DefaultRequestHeaders.Add("owner_id", "78c6beda-54a2-11ea-b064-0af3f8b02c24");
            client.DefaultRequestHeaders.Add("gstin", "29AAFCD5862R000");
            HttpResponseMessage response = await client.GetAsync(url);
            
            response.EnsureSuccessStatusCode(); // <= Will throw if unsuccessful
            using (FileStream fileStream = new FileStream(StrInvoiceNo.Replace("/","-") + ".pdf", FileMode.Create, FileAccess.Write, FileShare.None))
            {
                //copy the content from response to filestream
                await response.Content.CopyToAsync(fileStream);
                System.Diagnostics.Process.Start(StrInvoiceNo.Replace("/", "-") + ".pdf");
            }
        }

Just it's showing unexpected .whether this code support Vs 2010? — Materials, Sep 20 '20 at 01:04
It compiles just fine on my end. Definitely a framework problem — Ali Bdeir, Sep 20 '20 at 01:07
Duplicate of https://stackoverflow.com/questions/19423251/async-await-keywords-not-available-in-net-4-0 — Ali Bdeir, Sep 20 '20 at 01:08
I have only Vs 2010 license version.Is there any alternative code to do in Vs 2010.Please help how to use above code without async and wait keyword — Materials, Sep 20 '20 at 01:14

score 2 · Accepted Answer · answered Sep 20 '20 at 01:13

2

async and await have been introduced in C# 5. Visual Studio 2010 supports C# 4. Thats why you can't compile code with async/await under VS 2010.

answered Sep 20 '20 at 01:13

Lukasz Szczygielek

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Yes I know the above will not work in VS 2010.But please share and modify the above code without async and wait keyword to run in Vs 2010 – Materials Sep 20 '20 at 01:22
How to change this code – Materials Sep 20 '20 at 03:19
In your code you have for example method GetAsync which is not present in HttpClient in .Net 4, so it will be not trivial to change the code. – Lukasz Szczygielek Sep 20 '20 at 15:15

async not working with Visual Studio 2010 and .NET 4.0?

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