我们知道,在实现WCF传送二进制流数据这一操作过程中,会有一些限制因素。我们在实际应用中要特别注意这一点。今天我们就会针对这方面的问题做一个详细的介绍,希望对大家有所帮助。#t#
只有 BasicHttpBinding、WebHttpBinding、NetTcpBinding 和 NetNamedPipeBinding 支持传送流数据。
流数据类型必须是可序列化的 Stream 或 MemoryStream。
传递时消息体(Message Body)中不能包含其他数据。
我们先看看下面的WCF传送二进制流数据例子。
注意将 Binding.TransferMode 设置为 TransferMode.Streamed,我们还可以修改 Binding.MaxReceivedMessageSize 来调整消息大小(默认是64KB)。
- [ServiceContract]
- public interface IFileService
- {
- [OperationContract]
- void Upload(Stream stream);
- }
- public class FileService : IFileService, IDisposable
- {
- public void Upload(Stream stream)
- {
- FileStream file = new FileStream("test.dll", FileMode.Create);
- try
- {
- BinaryWriter writer = new BinaryWriter(file);
- BinaryReader reader = new BinaryReader(stream);
- byte[] buffer;
- do
- {
- buffer = reader.ReadBytes(1024);
- writer.Write(buffer);
- }
- while (buffer.Length > 0);
- }
- finally
- {
- file.Close();
- stream.Close();
- }
- }
- public void Dispose()
- {
- Console.WriteLine("Dispose...");
- }
- }
- public class WcfTest
- {
- public static void Test()
- {
- AppDomain.CreateDomain("Server").DoCallBack(delegate
- {
- ServiceHost host = new ServiceHost(typeof(FileService),
- new Uri("http://localhost:8080/FileService"));
- BasicHttpBinding binding = new BasicHttpBinding();
- binding.TransferMode = TransferMode.Streamed;
- host.AddServiceEndpoint(typeof(IFileService), binding, "");
- host.Open();
- });
- BasicHttpBinding binding2 = new BasicHttpBinding();
- binding2.TransferMode = TransferMode.Streamed;
- IFileService channel = ChannelFactory<IFileService>.
CreateChannel(binding2,- new EndpointAddress("http://localhost:8080/FileService"));
- using (channel as IDisposable)
- {
- FileStream stream = new FileStream("MyLibrary2.dll", FileMode.Open);
- channel.Test(stream);
- stream.Close();
- }
- }
- }
一切正常。那么 "传递时消息体(Memory Body)中不能包含其他数据" 是什么意思?我们修改一下上面的契约,除了传递文件流外,我们还希望传递文件名。
- [ServiceContract]
- public interface IFileService
- {
- [OperationContract]
- void Upload(string filename, Stream stream);
- }
- // ... 其他代码暂略 ...
当你修改完WCF传送二进制流数据的代码后,运行时你发现触发了一个 InvalidOperationException 异常。
未处理 System.InvalidOperationException
Message="For request in operation Upload to be a stream the operation must have a single parameter whose type is Stream."
Source="System.ServiceModel"
那么该怎么办呢?DataContract 肯定不行。 没错!你应该记得 MessageContract,将 filename 放到 MessageHeader 里面就行了。
- [MessageContract]
- public class FileData
- {
- [MessageHeader]public string filename;
- [MessageBodyMember]public Stream data;
- }
- [ServiceContract]
- public interface IFileService
- {
- [OperationContract]
- void Upload(FileData file);
- }
- public class FileService : IFileService, IDisposable
- {
- public void Upload(FileData file)
- {
- FileStream f = new FileStream(file.filename, FileMode.Create);
- try
- {
- BinaryWriter writer = new BinaryWriter(f);
- BinaryReader reader = new BinaryReader(file.data);
- byte[] buffer;
- do
- {
- buffer = reader.ReadBytes(1024);
- writer.Write(buffer);
- }
- while (buffer.Length > 0);
- }
- finally
- {
- f.Close();
- file.data.Close();
- }
- }
- public void Dispose(){
- Console.WriteLine("Dispose...");
- }
- }
- public class WcfTest
- {
- public static void Test()
- {
- AppDomain.CreateDomain("Server").DoCallBack(delegate
- {
- ServiceHost host = new ServiceHost(typeof(FileService),
- new Uri("http://localhost:8080/FileService"));
- BasicHttpBinding binding = new BasicHttpBinding();
- binding.TransferMode = TransferMode.Streamed;
- host.AddServiceEndpoint(typeof(IFileService), binding, "");
- host.Open();
- });
- BasicHttpBinding binding2 = new BasicHttpBinding();
- binding2.TransferMode = TransferMode.Streamed;
- IFileService channel = ChannelFactory<IFileService>.
CreateChannel(binding2,- new EndpointAddress("http://localhost:8080/FileService"));
- using (channel as IDisposable)
- {
- FileData file = new FileData();
- file.filename = "test2.dll";
- file.data = new FileStream("MyLibrary2.dll", FileMode.Open);
- channel.Upload(file);
- file.data.Close();
- }
- }
- }
问题解决了。上面的例子使用 BaseHttpBinding,如果使用 NetTcpBinding,相信速度要快很多。除了向服务器传送流外,也可反向返回流数据。
- [ServiceContract]
- public interface IFileService
- {
- [OperationContract]
- void Upload(Stream stream);
- [OperationContract]
- Stream Download(string filename);
- }
虽然服务器在操作结束时会自动关闭客户端 Request Stream,但个人建议还是使用 try...finnaly... 自主关闭要好一些,因为意外总是会发生的。
WCF传送二进制流数据的全部操作方法就为大家介绍到这里。