c# - 如何在 C# 中调用 Web 服务方法

Question

我想知道如何安全地调用 WCF 网络服务方法。这两种方法都可以接受/等效吗？有没有更好的办法？

第一种方式:

public Thing GetThing()
{
    using (var client = new WebServicesClient())
    {
        var thing = client.GetThing();
        return thing;
    }
}

第二种方式:

public Thing GetThing()
{
    WebServicesClient client = null;
    try
    {
        client = new WebServicesClient();
        var thing = client.GetThing();
        return thing;
    }
    finally
    {
        if (client != null)
        {
            client.Close();
        }
    }
}

我想确保客户端已正确关闭和处置。

谢谢

Answer 1

使用 using(没有双关语)是 not recommended因为即使 Dispose() 也会抛出异常。

下面是我们使用的几个扩展方法:

using System;
using System.ServiceModel;

public static class CommunicationObjectExtensions
{
    public static void SafeClose(this ICommunicationObject communicationObject)
    {
        if(communicationObject.State != CommunicationState.Opened)
            return;

        try
        {
            communicationObject.Close();
        }
        catch(CommunicationException ex)
        {
            communicationObject.Abort();
        }
        catch(TimeoutException ex)
        {
            communicationObject.Abort();
        }
        catch(Exception ex)
        {
            communicationObject.Abort();
            throw;
        }
    }

    public static TResult SafeExecute<TServiceClient, TResult>(this TServiceClient communicationObject, 
        Func<TServiceClient, TResult> serviceAction)
        where TServiceClient : ICommunicationObject
    {
        try
        {
            var result = serviceAction.Invoke(communicationObject);
            return result;
        } // try

        finally
        {
            communicationObject.SafeClose();
        } // finally
    }
}

有了这两个:

var client = new WebServicesClient();
return client.SafeExecute(c => c.GetThing());