c#从异步函数返回数据

发布时间：2020-12-15 23:32:28 所属栏目：百科来源：网络整理

导读：我有两种方法 public void GetEmp(){ HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new System.Uri("http://sdw2629/empservice/EmployeeInfo.svc/Employee")); request.Method = "GET"; request.ContentType = "application/json; char

我有两种方法

public void GetEmp()
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new System.Uri("http://sdw2629/empservice/EmployeeInfo.svc/Employee"));
    request.Method = "GET";
    request.ContentType = "application/json; charset=utf-8";

    request.BeginGetResponse(new AsyncCallback(ReadWebRequestCallback),request);  

}

和

private void ReadWebRequestCallback(IAsyncResult callbackResult)
{
    HttpWebRequest myRequest = (HttpWebRequest)callbackResult.AsyncState;
    using (HttpWebResponse myResponse = (HttpWebResponse)myRequest.EndGetResponse(callbackResult))
    {
        using (StreamReader httpwebStreamReader = new StreamReader(myResponse.GetResponseStream()))
        {
            string results = httpwebStreamReader.ReadToEnd();
            //execute UI stuff on UI thread.              
        }
    }
}

在这里,我想返回一个字符串“results”到这样的其他方法

string data= obj1.GetEmp()

我怎样才能实现这一目标..任何帮助都会得到满足……谢谢

解决方法

最简单的方法是使用async重写方法,如下所示：

public async Task<string> GetEmpAsync()
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new System.Uri("http://sdw2629/empservice/EmployeeInfo.svc/Employee"));
    request.Method = "GET";
    request.ContentType = "application/json; charset=utf-8";
    var response = await request.GetResponseAsync();
    using (StreamReader httpwebStreamReader = new StreamReader(response.GetResponseStream()))
    {
        string results = await httpwebStreamReader.ReadToEndAsync();
        //execute UI stuff on UI thread.
        return results;
    }

}

然后你可以得到这样的代码结果：

var results = await GetEmpAsync();

如果您使用的是旧版本并且没有异步,则可以通过阻止方式获取结果：

public string GetEmpBlocking()
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new System.Uri("http://sdw2629/empservice/EmployeeInfo.svc/Employee"));
    request.Method = "GET";
    request.ContentType = "application/json; charset=utf-8";
    var response = request.GetResponse();
    using (StreamReader httpwebStreamReader = new StreamReader(response.GetResponseStream()))
    {
        string results = httpwebStreamReader.ReadToEnd();
        //execute UI stuff on UI thread.
        return results;
    }
}

得到这样的结果：

var results = GetResultBlocking();

Р.S.您还可以考虑在早期版本中使用Microsoft.Bcl.Async来支持异步.

（编辑：李大同）

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