How To use ExecuteSqlCommandAsync

Question

I've been trying to figure out ExecuteSqlCommandAsync, which I haven't been able to find any good documentation on.

if (OldMarketRightsIDs.Count > 0)
{
    //This is where I want to have the task Begin        
    TaskReturn = Data.MK3Model.Database.ExecuteSqlCommandAsync("DELETE FROM TitleMarketRights WHERE ID in (" + string.Join(", ", OldMarketRightsIDs) + ")");
}

//This is the Code I want To execute in between
var NewMarketRights = MarketRights.Select(m => new
{
    Key = m.Key,
    Value = m.Value.Except(CurrentMarketRights[m.Key].Select(c => c.FK_ProductRight).ToList())
}).ToList();

foreach (var mr in NewMarketRights)
{
    foreach (var ProdID in mr.Value)
    {
        Data.MK3Model.TitleMarketRights.Add(new TitleMarketRight { FK_MarketID = (mr.Key == 0) ? null : (int?)mr.Key, FK_TitleID = ID, FK_ProductRight = ProdID });
    }
}

//This is where I want to wait until the task is complete before continuing
var i = await TaskReturn;

This Example doesn't compile, it gets an error await operator can only be used with an async Method. Any Ideas on how to get this working

Solution

Your code is fine. It just needs to be inside an async method:

public async Task FooAsync()
{
    if (OldMarketRightsIDs.Count > 0)
    {
        TaskReturn = Data.MK3Model.Database.ExecuteSqlCommandAsync("DELETE FROM TitleMarketRights WHERE ID in (" + string.Join(", ", OldMarketRightsIDs) + ")");
    }

    var NewMarketRights = MarketRights.Select(m => new
    {
        Key = m.Key,
        Value = m.Value.Except(CurrentMarketRights[m.Key].Select(c => c.FK_ProductRight).ToList())
    }).ToList();

    foreach (var mr in NewMarketRights)
    {
        foreach (var ProdID in mr.Value)
        {
            Data.MK3Model.TitleMarketRights.Add(new TitleMarketRight { FK_MarketID = (mr.Key == 0) ? null : (int?)mr.Key, FK_TitleID = ID, FK_ProductRight = ProdID });
        }
    }

    var i = await TaskReturn;
}

That's what allows you to use await. Behind the scenes a state machine is built that handles the asynchronous nature of you method. The method needs to have the async keyword and return a Task or Task<T> if you have a return value.

If you would want to have it as a lambda expression then:

Func<Task> fooAsync = async () =>
{
    if (OldMarketRightsIDs.Count > 0)
    {
        TaskReturn = Data.MK3Model.Database.ExecuteSqlCommandAsync("DELETE FROM TitleMarketRights WHERE ID in (" + string.Join(", ", OldMarketRightsIDs) + ")");
    }

    var NewMarketRights = MarketRights.Select(m => new
    {
        Key = m.Key,
        Value = m.Value.Except(CurrentMarketRights[m.Key].Select(c => c.FK_ProductRight).ToList())
    }).ToList();

    foreach (var mr in NewMarketRights)
    {
        foreach (var ProdID in mr.Value)
        {
            Data.MK3Model.TitleMarketRights.Add(new TitleMarketRight { FK_MarketID = (mr.Key == 0) ? null : (int?)mr.Key, FK_TitleID = ID, FK_ProductRight = ProdID });
        }
    }

    var i = await TaskReturn;
};

var task = fooAsync();