WCF run time exception.

Question

I am getting below error logged in log file.

Can any body hep me to come out.

 

Log file exception text:

 

 

<TraceRecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" Severity="Error">

<TraceIdentifier>http://msdn.microsoft.com/en-IN/library/System.ServiceModel.ServiceOperationExceptionOnReply.aspx</TraceIdentifier>

<Description>Replying to an operation threw a exception.</Description>

<AppDomain>DriveServerService.vshost.exe</AppDomain>

<Source>System.ServiceModel.Dispatcher.ImmutableDispatchRuntime/37425289</Source>

<Exception>

<ExceptionType>System.Runtime.Serialization.InvalidDataContractException, System.Runtime.Serialization, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType>

<Message>Type 'System.Collections.ArrayList+SyncArrayList' is an invalid collection type since it does not have a default constructor.</Message>

<StackTrace> at System.Runtime.Serialization.CollectionDataContract.GetValidContract(SerializationMode mode)

at System.Runtime.Serialization.DataContract.GetDataContract(RuntimeTypeHandle typeHandle, Type type, SerializationMode mode)