【Expression 序列化】WCF的簡單使用及其Expression Lambada的序列化問題初步解決方案（二）

 

接上文 【Expression 序列化】WCF的簡單使用及其Expression Lambada的序列化問題初步解決方案（一） 

上文留下了一個問題沒有處理，但最后也找到了相應的解決方案，下面就來說下問題的解決

Expression Tree Serializer 提供的解決方案是 把Expression表達式樹轉換為XElement類型的XML數據，傳輸到服務端，再反轉換還原成原來的Expression表達式

所以，客戶端與服務端之間傳送的數據是XElement類型的數據了，從而避開了Expression類型不能序列化的問題

我們先來了解一下Expression Tree Serializer的使用，下載 Expression Tree Serializer 源代碼進行編譯，只需要用到其中的ExpressionSerialization.dll

新建一個控制台項目，添加ExpressionSerialization引用。先來試用一下ExpressionSerialization對Expression的處理

把Main方法修改為如下代碼：

static void Main(string[] args)
{
    var sources = new[] { "abc", "abd", "bcd", "acd", "cdb" };
    Expression<Func<string, bool>> predicate = m => m.StartsWith("a");
    Console.WriteLine("使用原始Expression表達式查詢數據：");
    Console.WriteLine(predicate);
    sources.Where(predicate.Compile()).ToList().ForEach(s => Console.Write(s + " "));
    Console.WriteLine();
    var serializer = new ExpressionSerializer();
    var xmlPredicate = serializer.Serialize(predicate);
    var newPredicate = serializer.Deserialize<Func<string, bool>>(xmlPredicate);
    Console.WriteLine("使用新Expression表達式查詢數據：");
    Console.WriteLine(newPredicate);
    sources.Where(newPredicate.Compile()).ToList().ForEach(s => Console.Write(s + " "));
    Console.ReadLine();
}

注意：如提示無法生成請將控制台項目的“目標框架”由原來的“.NET Framework 4 Client Profie”修改為“.NET Framework 4”

運行控制台項目，得到如下結果，與預期一致：

有了成功的第一步，就敢大踏步往下走了，馬上對上一文中的代碼進行手術

對Services與Client項目分別添加ExpressionSerialization引用

WCF服務契約代碼修改為如下：

[ServiceContract]
public interface IAccountContract
{
    [OperationContract]
    Member GetMember(XElement xmlPredicate);
}

WCF服務實現代碼修改如下，為了在客戶端顯示服務端發生的異常信息，在服務實現類添加[ServiceBehavior(IncludeExceptionDetailInFaults = true)]特性：

[ServiceBehavior(IncludeExceptionDetailInFaults = true)]
public class AccountService : IAccountContract
{
    private readonly static List<Member> DataSource = new List<Member>
    {
        new Member {MemberID = 3, UserName = "zhangsan", Email = "[e-mail]"},
        new Member {MemberID = 4, UserName = "lisi", Email = "[e-mail]"},
        new Member {MemberID = 5, UserName = "wangwu", Email = "[e-mail]"},
        new Member {MemberID = 6, UserName = "zhaoliu", Email = "[e-mail]"}
    };

    public Member GetMember(XElement xmlPredicate)
    {
        var serializer = new ExpressionSerializer();
        var predicate = serializer.Deserialize<Func<Member, bool>>(xmlPredicate);
        return DataSource.SingleOrDefault(predicate.Compile());
    }
}

客戶端代碼修改如下：

static void Main(string[] args)
{
    Console.WriteLine("按任意建執行客戶端調用：");
    Console.ReadLine();
    try
    {
        Expression<Func<Member, bool>> predicate = m => m.UserName == "zhangsan";
        var serializer = new ExpressionSerializer();
        var xmlPredicate = serializer.Serialize(predicate);
        var result = WcfHelper.InvokeService<IAccountContract, Member>(wcf => wcf.GetMember(xmlPredicate));
        Console.WriteLine(result.Email);
    }
    catch (Exception e)
    {
        Console.WriteLine(e);
    }
    Console.ReadLine();
}

再次注意：如提示無法生成請將控制台項目的“目標框架”由原來的“.NET Framework 4 Client Profie”修改為“.NET Framework 4”

我們再次信心滿滿的修改多項目啟動，運行……服務端與客戶端都如願正常啟動了：

 

但是，客戶端按任意鍵執行調用的時候……客戶端發生了如下異常：

 

捕捉到 System.ServiceModel.FaultException<System.ServiceModel.ExceptionDetail>
  Message=Could not find a matching type
參數名: Liuliu.Wcf.IContract.Member
  Source=mscorlib
  Action=http://schemas.microsoft.com/net/2005/12/windowscommunicationfoundation/dispatcher/fault
  StackTrace:
    Server stack trace: 
       在 System.ServiceModel.Channels.ServiceChannel.ThrowIfFaultUnderstood(Message reply, MessageFault fault, String action, MessageVersion version, FaultConverter faultConverter)
       在 System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
       在 System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
       在 System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs)
       在 System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
       在 System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
    Exception rethrown at [0]: 
       在 System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
       在 System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
       在 Liuliu.Wcf.IContract.IAccountContract.GetMember(XElement xmlPredicate)
       在 Liuliu.Wcf.Client.Program.<>c__DisplayClass1.<Main>b__0(IAccountContract wcf) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.Client\Program.cs:行號 25
       在 Liuliu.Wcf.IContract.Helper.WcfHelper.InvokeService[TContract,TReturn](Func`2 func) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.IContract\Helper\WcfHelper.cs:行號 30
       在 Liuliu.Wcf.Client.Program.Main(String[] args) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.Client\Program.cs:行號 25
  InnerException: 

 

 

 

Liuliu.Wcf.IContract.Member類無法識別？！從客戶端傳過去的是數據是XElement的XML數據，因而ExpressionSerializer在進行反序列化操作的時候不知道有Liuliu.Wcf.IContract.Member這個類，知道大概也是只知其名而已
那就手動讓ExpressionSerializer去詳細了解Liuliu.Wcf.IContract.Member吧，萬般查找發現了KnownTypeExpressionXmlConverter這個類，看名就知道，就是干這個使的。
修改服務實現代碼如下：

public Member GetMember(XElement xmlPredicate)
{
    var assemblies = new List<Assembly> {typeof(Member).Assembly, typeof(ExpressionType).Assembly, typeof(IQueryable).Assembly};
    var resolver = new TypeResolver(assemblies, new[] {typeof(Member)});
    var knownTypeConverter = new KnownTypeExpressionXmlConverter(resolver);
    var serializer = new ExpressionSerializer(resolver, new CustomExpressionXmlConverter[] { knownTypeConverter });
    var predicate = serializer.Deserialize<Func<Member, bool>>(xmlPredicate);
    return DataSource.SingleOrDefault(predicate.Compile());
}

 客戶端代碼修改如下：

static void Main(string[] args)
{
    Console.WriteLine("按任意建執行客戶端調用：");
    Console.ReadLine();
    try
    {
        Expression<Func<Member, bool>> predicate = m => m.UserName == "zhangsan";
        var assemblies = new List<Assembly> { typeof(Member).Assembly, typeof(ExpressionType).Assembly, typeof(IQueryable).Assembly };
        var resolver = new TypeResolver(assemblies, new[] { typeof(Member) });
        var knownTypeConverter = new KnownTypeExpressionXmlConverter(resolver);
        var serializer = new ExpressionSerializer(resolver, new CustomExpressionXmlConverter[] { knownTypeConverter });
        var xmlPredicate = serializer.Serialize(predicate);
        var result = WcfHelper.InvokeService<IAccountContract, Member>(wcf => wcf.GetMember(xmlPredicate));
        Console.WriteLine(result.Email);
    }
    catch (Exception e)
    {
        Console.WriteLine(e);
    }
    Console.ReadLine();
}

 

再次運行，報如下異常：

捕捉到 System.ServiceModel.FaultException<System.ServiceModel.ExceptionDetail>
  Message=序列不包含任何元素
  Source=mscorlib
  Action=http://schemas.microsoft.com/net/2005/12/windowscommunicationfoundation/dispatcher/fault
  StackTrace:
    Server stack trace: 
       在 System.ServiceModel.Channels.ServiceChannel.ThrowIfFaultUnderstood(Message reply, MessageFault fault, String action, MessageVersion version, FaultConverter faultConverter)
       在 System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
       在 System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
       在 System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs)
       在 System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
       在 System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
    Exception rethrown at [0]: 
       在 System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
       在 System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
       在 Liuliu.Wcf.IContract.IAccountContract.GetMember(XElement xmlPredicate)
       在 Liuliu.Wcf.Client.Program.<>c__DisplayClass2.<Main>b__1(IAccountContract wcf) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.Client\Program.cs:行號 29
       在 Liuliu.Wcf.IContract.Helper.WcfHelper.InvokeService[TContract,TReturn](Func`2 func) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.IContract\Helper\WcfHelper.cs:行號 30
       在 Liuliu.Wcf.Client.Program.Main(String[] args) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.Client\Program.cs:行號 29
  InnerException: 

 

 

又查找了半天，沒發現原因，想想會不會是數據的發送與接收不一致了，加了個在客戶端發送前與服務端接收后都把相應的XElement數據寫入文本文件中，一對比，居然真的不一樣，吭爹啊……

 2.12KB VS 2.23KB

<LambdaExpression NodeType="Lambda" Name="" TailCall="false" CanReduce="false">
  <Type>
    <Type Name="System.Func`2">
      <Type Name="Liuliu.Wcf.IContract.Member" />
      <Type Name="System.Boolean" />
    </Type>
  </Type>
  <Parameters>
    <ParameterExpression NodeType="Parameter" Name="m" IsByRef="false" CanReduce="false">
      <Type>
        <Type Name="Liuliu.Wcf.IContract.Member" />
      </Type>
    </ParameterExpression>
  </Parameters>
  <Body>
    <BinaryExpression CanReduce="false" IsLifted="false" IsLiftedToNull="false" NodeType="Equal">
      <Right>
        <ConstantExpression NodeType="Constant" CanReduce="false">
          <Type>
            <Type Name="System.String" />
          </Type>
          <Value>zhangsan</Value>
        </ConstantExpression>
      </Right>
      <Left>
        <MemberExpression NodeType="MemberAccess" CanReduce="false">
          <Member MemberType="Property" PropertyName="UserName">
            <DeclaringType>
              <Type Name="Liuliu.Wcf.IContract.Member" />
            </DeclaringType>
            <IndexParameters />
          </Member>
          <Expression>
            <ParameterExpression NodeType="Parameter" Name="m" IsByRef="false" CanReduce="false">
              <Type>
                <Type Name="Liuliu.Wcf.IContract.Member" />
              </Type>
            </ParameterExpression>
          </Expression>
          <Type>
            <Type Name="System.String" />
          </Type>
        </MemberExpression>
      </Left>
      <Method MemberType="Method" MethodName="op_Equality">
        <DeclaringType>
          <Type Name="System.String" />
        </DeclaringType>
        <Parameters>
          <Type>
            <Type Name="System.String" />
          </Type>
          <Type>
            <Type Name="System.String" />
          </Type>
        </Parameters>
        <GenericArgTypes />
      </Method>
      <Conversion />
      <Type>
        <Type Name="System.Boolean" />
      </Type>
    </BinaryExpression>
  </Body>
  <ReturnType>
    <Type Name="System.Boolean" />
  </ReturnType>
</LambdaExpression>

 

<LambdaExpression NodeType="Lambda" Name="" TailCall="false" CanReduce="false" xmlns="">
  <Type>
    <Type Name="System.Func`2">
      <Type Name="Liuliu.Wcf.IContract.Member"></Type>
      <Type Name="System.Boolean"></Type>
    </Type>
  </Type>
  <Parameters>
    <ParameterExpression NodeType="Parameter" Name="m" IsByRef="false" CanReduce="false">
      <Type>
        <Type Name="Liuliu.Wcf.IContract.Member"></Type>
      </Type>
    </ParameterExpression>
  </Parameters>
  <Body>
    <BinaryExpression CanReduce="false" IsLifted="false" IsLiftedToNull="false" NodeType="Equal">
      <Right>
        <ConstantExpression NodeType="Constant" CanReduce="false">
          <Type>
            <Type Name="System.String"></Type>
          </Type>
          <Value>zhangsan</Value>
        </ConstantExpression>
      </Right>
      <Left>
        <MemberExpression NodeType="MemberAccess" CanReduce="false">
          <Member MemberType="Property" PropertyName="UserName">
            <DeclaringType>
              <Type Name="Liuliu.Wcf.IContract.Member"></Type>
            </DeclaringType>
            <IndexParameters></IndexParameters>
          </Member>
          <Expression>
            <ParameterExpression NodeType="Parameter" Name="m" IsByRef="false" CanReduce="false">
              <Type>
                <Type Name="Liuliu.Wcf.IContract.Member"></Type>
              </Type>
            </ParameterExpression>
          </Expression>
          <Type>
            <Type Name="System.String"></Type>
          </Type>
        </MemberExpression>
      </Left>
      <Method MemberType="Method" MethodName="op_Equality">
        <DeclaringType>
          <Type Name="System.String"></Type>
        </DeclaringType>
        <Parameters>
          <Type>
            <Type Name="System.String"></Type>
          </Type>
          <Type>
            <Type Name="System.String"></Type>
          </Type>
        </Parameters>
        <GenericArgTypes></GenericArgTypes>
      </Method>
      <Conversion></Conversion>
      <Type>
        <Type Name="System.Boolean"></Type>
      </Type>
    </BinaryExpression>
  </Body>
  <ReturnType>
    <Type Name="System.Boolean"></Type>
  </ReturnType>
</LambdaExpression>

 

對比以上數據可發現，

所有的空標簽發送時表示為<empty />的形式，而在接收后表示為<empty></empty>的形式，而ExpressionSerialization並沒有對這種情況進行處理

找到的問題所在，就能把問題解決掉

將ExpressionSerialization工程的ExpressionSerializer(Deserialize).cs 文件中的“if (xml.IsEmpty)”語句替換為“if (xml.IsEmpty || !xml.Elements().Any())”，共有3處，然后重新編譯ExpressionSerialization，添加引用

再次運行程序，終於得到期待已久的結果了：

現在可以高歌：紅軍不怕遠征難，萬水千山只等閑……

目前為此基本上解決了Expression序列化的問題了，可是……某日突然報了這么個異常：

 

捕捉到 System.ServiceModel.FaultException<System.ServiceModel.ExceptionDetail>
  Message=值不能為 null。
參數名: typeName
  Source=mscorlib
  Action=http://schemas.microsoft.com/net/2005/12/windowscommunicationfoundation/dispatcher/fault
  StackTrace:
    Server stack trace: 
       在 System.ServiceModel.Channels.ServiceChannel.ThrowIfFaultUnderstood(Message reply, MessageFault fault, String action, MessageVersion version, FaultConverter faultConverter)
       在 System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
       在 System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
       在 System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs)
       在 System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
       在 System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
    Exception rethrown at [0]: 
       在 System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
       在 System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
       在 Liuliu.Wcf.IContract.IAccountContract.GetMember(XElement xmlPredicate)
       在 Liuliu.Wcf.Client.Program.<>c__DisplayClass4.<Main>b__2(IAccountContract wcf) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.Client\Program.cs:行號 37
       在 Liuliu.Wcf.IContract.Helper.WcfHelper.InvokeService[TContract,TReturn](Func`2 func) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.IContract\Helper\WcfHelper.cs:行號 30
       在 Liuliu.Wcf.Client.Program.Main(String[] args) 位置 D:\我的文檔\Visual Studio 2010\Projects\LambadaSerializeDemo\Liuliu.Wcf.Client\Program.cs:行號 37
  InnerException: 

 

而發生異常的場景是這樣的，在客戶端代碼添加了一個輸入字符串作為查詢條件的一部分（17行）：

客戶端代碼：

static void Main(string[] args)
{
    Console.WriteLine("按任意建執行客戶端調用：");
    Console.ReadLine();
    try
    {
        Expression<Func<Member, bool>> predicate = m => m.UserName == "zhangsan";
        Console.WriteLine(predicate);
        var assemblies = new List<Assembly> { typeof(Member).Assembly, typeof(ExpressionType).Assembly, typeof(IQueryable).Assembly };
        var resolver = new TypeResolver(assemblies, new[] { typeof(Member) });
        var knownTypeConverter = new KnownTypeExpressionXmlConverter(resolver);
        var serializer = new ExpressionSerializer(resolver, new CustomExpressionXmlConverter[] { knownTypeConverter });
        var xmlPredicate = serializer.Serialize(predicate);
        var result = WcfHelper.InvokeService<IAccountContract, Member>(wcf => wcf.GetMember(xmlPredicate));
        Console.WriteLine(result.Email);

        var input = Console.ReadLine();
        if (!string.IsNullOrEmpty(input))
        {
            predicate = m => m.UserName == input;
            Console.WriteLine(predicate);
            xmlPredicate = serializer.Serialize(predicate);
            result = WcfHelper.InvokeService<IAccountContract, Member>(wcf => wcf.GetMember(xmlPredicate));
            Console.WriteLine(result.Email);
        }
    }
    catch (Exception e)
    {
        Console.WriteLine(e);
    }
    Console.ReadLine();
}

 

這樣一個很正常的需求，居然又引出了一個大問題，詳情請聽下回分解^_^

 

 本文源代碼下載：LambadaSerializeDemo02.rar