/// <summary>Creates and executes a DataServiceQuery based on the passed in expression which results a single value</summary>
/// <typeparam name="TElement">generic type</typeparam>
/// <param name="expression">The expression for the new query</param>
/// <returns>single valued results</returns>
internal TElement ReturnSingleton <TElement>(Expression expression)
{
IQueryable <TElement> query = new DataServiceQuery <TElement> .DataServiceOrderedQuery(expression, this);
MethodCallExpression mce = expression as MethodCallExpression;
Debug.Assert(mce != null, "mce != null");
SequenceMethod sequenceMethod;
if (ReflectionUtil.TryIdentifySequenceMethod(mce.Method, out sequenceMethod))
{
switch (sequenceMethod)
{
case SequenceMethod.Single:
return(query.AsEnumerable().Single());
case SequenceMethod.SingleOrDefault:
return(query.AsEnumerable().SingleOrDefault());
case SequenceMethod.First:
return(query.AsEnumerable().First());
case SequenceMethod.FirstOrDefault:
return(query.AsEnumerable().FirstOrDefault());
#if !ASTORIA_LIGHT
case SequenceMethod.LongCount:
case SequenceMethod.Count:
return((TElement)Convert.ChangeType(((DataServiceQuery <TElement>)query).GetQuerySetCount(this.Context), typeof(TElement), System.Globalization.CultureInfo.InvariantCulture.NumberFormat));
#endif
default:
throw Error.MethodNotSupported(mce);
}
}
// Should never get here - should be caught by expression compiler.
Debug.Assert(false, "Not supported singleton operator not caught by Resource Binder");
throw Error.MethodNotSupported(mce);
}
internal override Expression VisitMethodCall(MethodCallExpression m)
{
throw Error.MethodNotSupported(m);
}