Context message for UPDATE is not working

Question

I am working on a CRM Dynamics Plugin. There is a field on custom entity named "email". I want to make sure that for two entity records email addresses should be unique. For that purpose I have written following code:

public class Class1 : IPlugin
{
    public void Execute(IServiceProvider serviceProvider)
    {
        // Obtain the execution context from the service provider.
        Microsoft.Xrm.Sdk.IPluginExecutionContext context = (Microsoft.Xrm.Sdk.IPluginExecutionContext)
            serviceProvider.GetService(typeof(Microsoft.Xrm.Sdk.IPluginExecutionContext));

        // Get a reference to the organization service.
        IOrganizationServiceFactory factory =
        (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
        IOrganizationService service = factory.CreateOrganizationService(context.UserId);


        // The InputParameters collection contains all the data passed in the message request.
        if (context.InputParameters.Contains("Target") &&
            context.InputParameters["Target"] is Entity)
        {
            Entity entity = (Entity)context.InputParameters["Target"];

            //</snippetAccountNumberPlugin2>

            // Verify that the target entity represents an account.
            // If not, this plug-in was not registered correctly.
            if (context.MessageName.ToUpper() == "CREATE")
            {
                if (entity.LogicalName == "new_assignment1entity")
                {
                    try
                    {
                        QueryExpression query = new QueryExpression("new_assignment1entity");
                        query.ColumnSet.AddColumns("new_email");
                        EntityCollection result1 = service.RetrieveMultiple(query);
                        foreach (var a in result1.Entities)
                        {
                            int size = result1.Entities.Count;
                            if (a.Attributes["new_email"].ToString().Equals(entity["new_email"]))
                                throw new InvalidPluginExecutionException("Duplicate Email found!");
                        }
                    }
                    catch (FaultException<Microsoft.Xrm.Sdk.OrganizationServiceFault>)
                    {
                        //You can handle an exception here or pass it back to the calling method.
                        throw new InvalidPluginExecutionException("Some problem occurred while Querying Records!");
                    }
                }
            }
            else if (context.MessageName.ToUpper() == "UPDATE")
            {
                if (entity.LogicalName == "new_assignment1entity")
                {
                    try
                    {
                        QueryExpression query = new QueryExpression("new_assignment1entity");
                        query.ColumnSet.AddColumns("new_email");
                        EntityCollection result1 = service.RetrieveMultiple(query);
                        foreach (var a in result1.Entities)
                        {
                            int size = result1.Entities.Count;
                            if (a.Attributes["new_email"].ToString().Equals(entity["new_email"]))
                                throw new InvalidPluginExecutionException("Duplicate Email found!");
                        }
                    }
                    catch (FaultException<Microsoft.Xrm.Sdk.OrganizationServiceFault>)
                    {
                        //You can handle an exception here or pass it back to the calling method.
                        throw new InvalidPluginExecutionException("Some problem occurred while Querying Records!");
                    }
                }
            }
        }
    }
}

When User creates a new entity record with duplicate email address this code works and shows a dialog box printing error message. But when User edit an existing record (update and existing record) and makes the email address duplicate then this code does not work and updated record with duplicated email address saved.
I am guessing that Context message with UPDATE else part is not working.
Please help me out.

Answer 1

I resolved this issue. The problem why only Create execution flow was running and not Update is that I had only registered the plugin for create message step. To overcome this issue, I added a new step in same plugin and registered it with update message as show in following screenshot:

And it worked like charm.

Apart from this, @GregOwens mentioned very helpful points.These should follow as best practices in CRM Development.

Answer 2

It's not really worth trying to debug this as unfortunately you are going about this in a horribly inefficient way. (Though the most likely cause is the way you are querying being subject to a "feature" of CRM which means you are not querying all the records you think you are).

In short, your code says:

• Get me ALL(*) instances of the new_assignment1entity entity
• Look at each record until I find one with an email address that matches (case-sensitive) the value just provided in the update
• Throw an exception when you encounter the first exact match (otherwise continue with the transaction)

Mains points of note:

1. QueryExpression will only return the maximum first 5000 records in CRM
2. You should be filtering your query to only return new_assignment1entity records where the new_email attribute matches the provided value
3. String.Equals(string) is case-sensitive so to truly check for a duplicate, you should convert the case of each value
4. Your size variable serves no purpose
5. Your code will throw an exception if the new/updated record has no value for new_email. You should check that the attribute exists before attempting to access it