如何使用ExecuteSqlCommandAsync

Question

我一直想弄明白ExecuteSqlCommandAsync,我一直无法找到任何好的文档.

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;

这个例子没有编译,它得到一个错误await运算符只能与async方法一起使用.关于如何使这个工作的任何想法

Answer 1

你的代码很好.它只需要在一个async方法内:

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;
}

这就是允许你使用的东西await.在幕后,构建了一个状态机,用于处理方法的异步特性.该方法需要具有async关键字并返回a Task或者Task<T>如果您有返回值.

如果你想将它作为lambda表达式,那么:

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();