Making a normal method asynchronous in c#

Question

I have a method in c#:

public DataSet OpenSqlQuery(string SqlQuery)
{
    con = new SqlConnection(connection_string);
    con.Open();
    var sqlc = new SqlCommand(SqlQuery, con);
    da = new SqlDataAdapter(sqlc);
    var ds = new DataSet();
    da.Fill(ds);
    con.Close();
    return ds;
}

Now I want to make it as an asynchronous method so I can call it by await. so I changed it to:

public async Task<DataSet> OpenSqlQuery(string SqlQuery)
{
    con = new SqlConnection(connection_string);
    con.Open();
    var sqlc = new SqlCommand(SqlQuery, con);
    da = new SqlDataAdapter(sqlc);
    var ds = new DataSet();
    await da.Fill(ds);
    con.Close();
    return ds;
}

I set await before da.Fill(ds) because at this line, the program waits for server. But the function shows this error:

'int' does not contain a definition for 'GetAwaiter' and no extension method 'GetAwaiter' accepting a first argument of type 'int' could be found (are you missing a using directive or an assembly reference?)

How can I make this method asynchronous?

P.S: The main goal is to call this method as follows:

Dataset ds = await objConnect.OpenSqlQuery(query);

P.S: Difference between this question and possible dupplicated one is that this post about making an existing synchronous method to asynchronous, while another is about making an asynchronous method.

Possible duplicate of [How do you create an asynchronous method in C#?](http://stackoverflow.com/questions/16063520/how-do-you-create-an-asynchronous-method-in-c) — Smartis has left SO again, May 02 '17 at 09:37
Look at the `Task` class, f.e.[`Task.Run`](https://msdn.microsoft.com/en-us/library/hh195051(v=vs.110).aspx) — Tim Schmelter, May 02 '17 at 09:39
As a side-note: you should use the `using`-statement to dispose the connection as soon as you're finished with it. I would not store it in a field of the class. — Tim Schmelter, May 02 '17 at 09:41
@Tim, As I found, `Task.Run` is used when we wait for our program to end, not other programs. isn't it? — Alireza Zojaji, May 02 '17 at 09:42
@Tim, Because I want to remain the form responsive during the query executes. — Alireza Zojaji, May 02 '17 at 09:44
Isn't Fill going to be called sychronously anyway? Why not use SqlDataReader and get Access to Reader.ReadAsync and SqlCommand.ExecuteReaderAsync ? Then you can do Async properly. — Stuart, May 02 '17 at 09:45
@Stuart, `Fill` is the main time consuming method in this function. when I made it synchronous, what is the benefit of `async`? — Alireza Zojaji, May 02 '17 at 09:46
@Ernis - `async` methods construct the `Task` wrapper automatically. Seriously, this feature has existed for a fair few years now. — Damien_The_Unbeliever, May 02 '17 at 09:56
It should also be noted that this method, in general, represents a bit of an anti-pattern. You're forcing callers to only work in terms of a string query and so precluding any use of parameters, opening yourself if for SQL Injection attacks. — Damien_The_Unbeliever, May 02 '17 at 09:59
@AmirZojaji: Is this running in a UI context, as part of an ASP.NET request, or in a background thread? — Stephen Cleary, May 02 '17 at 12:59
@Stephen, This is inside a UI and I need `await` to make the form responsive during query execution. — Alireza Zojaji, May 02 '17 at 13:20
@AmirZojaji: In that case, the `Task.Run` solution is appropriate. — Stephen Cleary, May 02 '17 at 13:40

Making a normal method asynchronous in c#

0 Answers0