Getting NullReferenceException when calling WCF service from client - wcf

Question

The method that I am trying to call has the following signature:
Results GetPerformanceData(MyEntity entity, bool recurse);
I set a breakpoint at the beginning of the method, but the exception is thrown before code execution gets to the breakpoint.
Tracing the WCF service gives me the following info:
System.NullReferenceException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Object reference not set to an instance of an object.
StackTrace:
at System.Runtime.Serialization.CodeGenerator.VerifyParameterCount(MethodInfo methodInfo, Int32 expectedCount)
at System.Runtime.Serialization.CodeGenerator.Call(Object thisObj, MethodInfo methodInfo, Object param1)
at ...
How can I determine what the null variable is? I have my debugger set to break on all exceptions, but it isn't breaking for this particular problem. It looks like the "entity" parameter to the method I am trying to call cannot deserialize properly.
Sample invocation call
var results = client. GetPerformanceData(entity, true);
WCF service config
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<system.diagnostics>
<sources>
<source name="System.ServiceModel"
switchValue="All"
propagateActivity="true">
<listeners>
<add name="traceListener"
type="System.Diagnostics.XmlWriterTraceListener"
initializeData= "trace.svclog" />
</listeners>
</source>
</sources>
</system.diagnostics>
<system.serviceModel>
<bindings>
<basicHttpBinding>
<binding name="basicHttpBindingSettings" closeTimeout="00:01:00"
openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"
allowCookies="false" bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard"
maxBufferSize="5242880" maxBufferPoolSize="52428800" maxReceivedMessageSize="5242880"
messageEncoding="Text" textEncoding="utf-8" transferMode="Buffered"
useDefaultWebProxy="true">
<readerQuotas maxDepth="64" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
</binding>
</basicHttpBinding>
</bindings>
<services>
<service name="Company.Service.Engine"
behaviorConfiguration="ServiceBehavior">
<host>
<baseAddresses>
<add baseAddress="http://localhost:8000/Engine"/>
</baseAddresses>
</host>
<endpoint address=""
binding="basicHttpBinding"
bindingConfiguration="basicHttpBindingSettings"
contract="Company.Service.IEngine"/>
<endpoint address="mex"
binding="mexHttpBinding"
contract="IMetadataExchange" />
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="ServiceBehavior">
<serviceMetadata httpGetEnabled="true"/>
<serviceDebug includeExceptionDetailInFaults="True"/>
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
</configuration>

Answer 1

It turns out that I had some properties tagged as [DataMember] that had getters but no setters.
Usually, I'd get a descriptive error by looking at the trace file on the service, or in a pop-up window when adding the service reference on the client project. This time around I did not.
I had to search for ALL instances of [DataMember] and looked at them one by one to find the properties that were missing a setter.

Answer 2

I know this question is old but if somebody else stumbles upon this question this might help in solving the problem
I just had this problem and discovered something new about the [DataMember] Annotation, I had 2 classes and one of these classes had a reference to the other(let's call them class A and B), where some of the properties and fields in class B was referred to in class A.
here's a little example of what I had
[DataContract]
public class A
{
[Datamember]
public B classb {get;set;}
[DataMember]
public int Number
{
get {return classb.Number;}
set {classb.Number = value;}
}
}
[DataContract]
public class B
{
[DataMember]
public int Number
{
get;
set;
}
}
the thing is that the null reference was there because datamember means that itself holds a value where class A just holds a reference to the number in class B, what you do now is put a Datamember on only one of the numbers.

Answer 3

I was also getting a NullReferenceException from System.Runtime.Serialization.CodeGenerator.VerifyParameterCount when I changed the concrete type passed to a data contract, to one that was missing the [DataContract] attribute.
[DataContract, KnownType(typeof(NewEngine))]
public class Car
{
[DataMember]
public IEngine Engine { get; set; }
}
[DataContract] // DON'T FORGET THIS
public class NewEngine : IEngine { ... }

Answer 4

I found another cause for that error: assigning the same DataMember.Name to two properties caused the error for me:
[DataContract]
public class Car
{
[DataMember(Name = "Type")]
public string EngineType { get; set; }
[DataMember(Name = "Type")]
public string TyresType { get; set; }
}
I know it is a big mistake but, if the properties are many... it could happen :-)

Answer 5

There could be several issues here. Make sure your datacontracts have the proper attributes. Make sure your service references are up to date, and if not reusing your datacontracts by referencing the assemblies make sure the generation of the objects is correct (the generated code is usually in a file called Reference.cs). also try placing a try catch block around every service operation and wrap those exceptions in FaultExceptions. This could help you find a better answer.
try
{
...
}
catch (Exception ex)
{
// The generic argument might be unnecessary
throw new FaultException<Exception>(ex);
}