FromAsync的BeginXXX参数太多

本文关键字：太多 参数 BeginXXX FromAsync | 更新日期: 2023-09-27 18:05:19

我有一个异步方法，签名如下:

IAsyncResult BeginGetMyNumber(string foo, string bar, string bat, int bam, AsyncCallback callback, object state)

我想用Factory执行它。fromsync:

var result  = Task<int>.Factory.FromAsync(
                instance.BeginGetMyNumber, 
                instance.EndGetMyNumber, 
                "foo",
                "bar",
                "bat",
                100, /*bam*/
                null);

，但我得到以下错误:

参数1:不能从'method group'转换为的系统。函数'

似乎没有合适的重载FromAsync方法http://msdn.microsoft.com/en-us/library/system.threading.tasks.taskfactory.fromasync.aspx，它只支持在BeginXXX方法上最多5个参数(包括回调和状态)。

除了重构BeginXXX方法使其接受一个对象而不是六个参数之外，是否有一种方法可以使用FromAsync执行它?

FromAsync的BeginXXX参数太多

result = Task<string>.Factory.FromAsync(
  (callback, state) => instance.BeginGetMyNumber("foo", "bar", "bat", 1, callback, state),
   instance.EndGetMyNumber, state: null);

此技术(部分函数应用)适用于具有任意数量输入参数的begin方法。

实际上，我似乎可以使用工厂的重载方法。FromAsync(以IAsyncResult对象作为第一个参数，以回调方法作为第二个参数):

result = Task<string>.Factory.FromAsync(
                instance.BeginGetMyNumber("foo", "bar", "bat", 1, null, null),
                instance.EndGetMyNumber);

基本上，你已经用完了参数。(

FromAsync方法最多只接受三个传递给异步调用的参数，完整地拼写如下:

var result  = Task<int>
    .Factory
    .FromAsync<string,string,string>(
        BeginGetMyNumber,
        EndGetMyNumber,
        "foo",
        "bar",
        "bat",
        null);

如果你有:

IAsyncResult BeginGetMyNumber(
   string foo, 
   string bar, 
   string bat, 
   AsyncCallback callback, 
   object state)
{
}

但是你喝多了。

哦，有些东西可能会有所帮助- 你会想要清理这个，这是非常拼凑的!!

public static class Ext
{
    public static Task<TResult> FromAsync<TArg1, TArg2, TArg3, TArg4, TResult>(
        this TaskFactory<TResult> factory,
        Func<TArg1,TArg2,TArg3,TArg4,AsyncCallback, object, IAsyncResult> beginMethod, 
        Func<IAsyncResult, TResult> endMethod, 
        TArg1 arg1,
        TArg2 arg2,
        TArg3 arg3,
        TArg4 arg4,
        object state,
        TaskCreationOptions creationOptions = TaskCreationOptions.None, 
        TaskScheduler scheduler = null)
    {
        scheduler = scheduler ?? TaskScheduler.Current;
        AsyncCallback callback = null;
        if (beginMethod == null)
        {
            throw new ArgumentNullException("beginMethod");
        }
        if (endMethod == null)
        {
            throw new ArgumentNullException("endMethod");
        }
        TaskCompletionSource<TResult> tcs = 
             new TaskCompletionSource<TResult>(state, creationOptions);
        try
        {
            if (callback == null)
            {
                callback = delegate (IAsyncResult iar) 
                {
                    tcs.TrySetResult(endMethod(iar));
                };
            }
            beginMethod(arg1, arg2, arg3, arg4, callback, state);
        }
        catch
        {
            tcs.TrySetResult(default(TResult));
            throw;
        }
        return tcs.Task;
    } 
}
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