CODEWITHSUNDEEP
c#winformsasync-awaitbegininvoke
Ivan
Ivan

Reputation: 7746

Convert BeginInvoke to async/await

I have a function apiClient.OrderSend that must be called inside the "GUI" thread, so I created this function

   private void RunOnUIThread(Action action)
   {
        this.BeginInvoke(action);
   }

I then have a function that needs to return an int like this

    int AlgoSendOrder(MT4Order order)
    {
        int retVal = -1;

        RunOnUIThread(() =>
        {
            retVal = apiClient.OrderSend(order.Symbol, (TradeOperation)order.OrderSide, order.Volume,
                                        order.Price, order.AllowedSlippage ?? default(int),
                                        order.PriceToStopLoss ?? default(double),
                                        order.PriceToTakeProfit ?? default(double));
        });

        return retVal;
    }

The problem is that AlgoSendOrder returns before apiClient.OrderSend returns, so retVal is always -1 to the client of this function.

It seems that this a reasonable change is to use await-async pair execute the function in the GUI thread, and to have the desired effect of waiting for the return value. However I can't seem to get it to work.

Seems like I should be able to rework RunOnUIThread to use async-await

public async Task RunOnUIThreadAsync()
{
    if (InvokeRequired)
    {
        // what do I put here?
    }
    {
        … // like before (but can now use `await` expressions)
    }
}

Upvotes: 3

Views: 4596

Answers (1)

Philippe Paré
Philippe Paré

Reputation: 4418

Use an async method to perform the background task in a separate thread. Note the Task.Run in the sample below:

async Task<int> AlgoSendOrderAsync(MT4Order order)
{
    int retVal = -1;

    //Doing this on another thread using Task.Run
    await Task.Run(() =>
    {
        retVal = apiClient.OrderSend(order.Symbol, (TradeOperation)order.OrderSide, order.Volume,
                                    order.Price, order.AllowedSlippage ?? default(int),
                                    order.PriceToStopLoss ?? default(double),
                                    order.PriceToTakeProfit ?? default(double));
    });

    return retVal;
}

Call this method on the UI thread like this:

async void onButtonClickOnWhatever(object sender, EventArgs args)
{
    int result = await AlgoSendOrderAsync(order);
    //Here you are on the UI thread, you can update your controls here safely
}

Upvotes: 5

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