Custom entities and attributes in a plug-in

You cannot create a webservice in Visual Studio when you're writing a plugin. Instead you need to use the method context.CreateCrmService(true);. There is only one single issue when using this approach. You cannot leverage the power of IntelliSense in Visual Studio. Visual Studio will not recognize your custom entities and attributes. How to work with this? The only correct answer is "Dynamic Entities".

To retrieve records based on some attribute values you could use a piece of code like this:

// Create the QueryByAttribute object.
QueryByAttribute query = new QueryByAttribute();
query.ColumnSet = new AllColumns();
query.EntityName = "new_customentity";
query.Attributes = new string[] { "new_customentityid" };
query.Values = new string[] { customEntityId };

// Create the request.
RetrieveMultipleRequest request = new RetrieveMultipleRequest();

// Set the request properties.
request.Query = query;
request.ReturnDynamicEntities = true;

// Execute the request.
RetrieveMultipleResponse response = (RetrieveMultipleResponse)service.Execute(request);

One of the most important details in this piece of code is this line:

request.ReturnDynamicEntities = true;

If you forget this line, you'll end up with this error message:

System.InvalidOperationException was unhandled by user code Message="There is an error in XML document (1, 509)." Source="System.Xml" StackTrace: at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle) at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) at Microsoft.Crm.SdkTypeProxy.CrmService.Execute(Request Request) at Microsoft.Crm.Asynchronous.SdkTypeProxyCrmServiceWrapper.Execute(Object request) at ...your assembly information...

So, don't forget the ReturnDynamicEntities attribute and you should be fine to go!