C＃（异步/等待）在任务块中循环我的主线程？

Question

private async Task<PortalODataContext> CallConnection(Connection connection)
    {
        bool cancel = false;
        connection.Connected = true;
        var task = getConnection(connection);

        while (!cancel && !task.IsCompleted)
        {
            Thread.Sleep(100);

            if (connection.Disconected)
            {
                cancel = true;
            }
        }

        return await task;
    }

That is my function that I call on the main thread Like so :

PortalODataContext portalContext = await this.CallConnection(connectionOpen);

I am new to async and await so I'm just trying to figure out why My task"CallConnection" block my main UI thread ... can you guys help me ?

Ohh and there is the GetConnection :

private Task<PortalODataContext> getConnection(Connection connection)
    {            
        return Task.Factory.StartNew(() =>
        {
            try
            {
                var context = connection.ConnectToPortal();
                connection.ListTemplateLib = this.ShellModel.ConnectionManager.GetTemplateLibrarys(connection);
                connection.ListTemplateGrp = this.ShellModel.ConnectionManager.GetTemplateGroups(connection, connection.TemplateLibraryId);
                connection.ListTemplates = this.ShellModel.ConnectionManager.GetTemplates(connection, connection.TemplateGroupId);
                return context;
            }
            catch (Exception)
            {
                throw;
            }
       });

Thanks in advance

Answer 1

Becasue the Thread.Sleep

async/await split your method in two, before and after the await . In the first half you have a Thread.Sleep , causing the caller thread to freeze.

Use:

private async Task<PortalODataContext> CallConnection(Connection connection)
{
    bool cancel = false;
    connection.Connected = true;
    var task = getConnection(connection);

    while (!cancel && !task.IsCompleted)
    {
        await Task.Delay(100);

        if (connection.Disconected)
        {
            cancel = true;
        }
    }

    return await task;
}

I am not completely sure what you are trying to achieve here.

Answer 2

When you call an async task , you have to wait for a result.

The benefit of asyncs is that you can run two processes in a method, but just inside that method. Before you leave that block both processes must be unified again. That makes you easier to run different processes not having to write delegates and Locks for objects involved.

Take a look here to see what happens in an async methods. There is a diagram there that can help you to clarify the flow.

In your code you don't need the Threed.Sleep. The CallConnection method won't return anything until getConnection returns something. Then you can continue in your main Thread.

Hope that help you.