Question

I suspect I’m missing something rather basic, yet I can’t figure this one out.

I’m running a simple linq query –

var result = from UserLine u in context.Users 
             where u.PartitionKey == provider.Value && u.RowKey == id.Value 
             select u;
        UserLine user = null;
        try
        {
            user = result.FirstOrDefault();

        }

For some reason this produces a TargetInvocationException with an inner exception of NullReferenceException.

This happens when the linq query produces no results, but I was under the impression that FirstOrDefault would return Default<T> rather than throw an exception?

I don’t know if it matters, but the UserLine class inherits from Microsoft.WindowsAzure.StorageClient.TableServiceEntity

Answer 1

I figured it out – the problem occured when either id or provider had ‘/’ in the value, which the id did. when I removed it the code ran fine

Understanding the Table Service Data Model has a section on ‘Characters Disallowed in Key Fields’ –

The following characters are not allowed in values for the
PartitionKey and RowKey properties:

• The forward slash (/) character
• The backslash () character
• The number sign (#) character
• The question mark (?) character