利用反射改变WCF dataContractSerializer属性
在WCF的使用过程中，有时会碰到传递的数据量比较巨大，客户端程序报错。常见的解决方法就是通过增大改变服务端与客户端配置文件serviceBehaviors的dataContractSerializer 的maxItemsInObjectGraph属性。有没有不通过配置文件，直接硬编码增大maxItemsInObjectGraph的值呢（此文不是考虑那种做法的优劣，而仅仅是探讨一种可能）？答案是肯定的。方法如下。
既然wcf的maxItemsInObjectGraph可以通过配置去设定，那么应该也有可能通过代码去设定。因为maxItemsInObjectGraph 通过配置文件信息的读取到这个信息后，最终应该把读到的信息去设置某个类的属性，从而改变服务的配置。
1. 先从有配置文件时，服务的运行开始着手。服务端配置文件如下
<behaviors>
<serviceBehaviors>
<behavior name="Service1Behavior">
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="true" />
<dataContractSerializer maxItemsInObjectGraph="2147483647" />
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
在ServiceHost实例化完成后加入如下的代码：
public void Start()
{
ServiceHost host = new ServiceHost(typeof(Service1));
Console.WriteLine("---------------------------------");
foreach (var item in host.Description.Behaviors)
{
Console.WriteLine(item.ToString());
}
Console.WriteLine("---------------------------------");
host.Open();
}
在输出窗口得到以下信息：
---------------------------------
System.ServiceModel.ServiceBehaviorAttribute
Microsoft.VisualStudio.Diagnostics.ServiceModelSink.Behavior
System.ServiceModel.Description.ServiceMetadataBehavior
System.ServiceModel.Description.ServiceDebugBehavior
System.ServiceModel.Dispatcher.DataContractSerializerServiceBehavior
System.ServiceModel.Description.ServiceAuthorizationBehavior
进一步跟踪得知。dataContractSerializer对应的类就是DataContractSerializerServiceBehavior。
2. 构造DataContractSerializerServiceBehavior实例，设置maxItemsInGraph属性，并把实例插入host.Description.Behaviors中。
用reflector 查看DataContractSerializerServiceBehavior,发现声明如下
internal class DataContractSerializerServiceBehavior£ºIServiceBehavior, IEndpointBehavior{}
看来只能用反射类实例化它了。具体代码如下： ServiceHost host = new ServiceHost(typeof(Service1));
Type t = host.GetType();
object obj= t.Assembly.CreateInstance("System.ServiceModel.Dispatcher.DataContractSerializerServiceBehavior",
true,BindingFlags.CreateInstance|BindingFlags.Instance|BindingFlags.NonPublic ,null,new object[]{false ,Int32.MaxValue },null,null);
IServiceBehavior myServiceBehavior=obj as IServiceBehavior ;
if (myServiceBehavior != null)
{
host.Description.Behaviors.Add(myServiceBehavior);
}
Console.WriteLine("---------------------------------");
foreach (var item in host.Description.Behaviors)
{
Console.WriteLine(item.ToString());
}
Console.WriteLine("---------------------------------");
host.Open(); 3. 然后注释掉配置文件的dataContractSerializer
<behaviors>
<serviceBehaviors>
<behavior name="Service1Behavior">
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="true" />
<!--<dataContractSerializer maxItemsInObjectGraph="2147483647" />-->
</behavior>
</serviceBehaviors>
</behaviors>
4. 经测试，硬编码设置maxItemsInObjectGraph,与设置配置文件的属性能达到同样的效果
