/// <summary>
/// Filters the elements of <paramref name="source"/> based on <paramref name="targetResourceType"/>
/// </summary>
/// <param name="source">source</param>
/// <param name="targetResourceType">targetResourceType</param>
/// <returns>An expression for IEnumerable(Of T) that contains elements from the source sequence of type <paramref name="targetResourceType"/>.</returns>
internal static Expression GenerateOfType(Expression source, ResourceType targetResourceType)
{
if (targetResourceType.CanReflectOnInstanceType)
{
return(source.EnumerableOfType(targetResourceType.InstanceType));
}
source = Expression.Call(
DataServiceProviderMethods.OfTypeIEnumerableMethodInfo.MakeGenericMethod(
BaseServiceProvider.GetIEnumerableElement(source.Type),
targetResourceType.InstanceType),
source,
Expression.Constant(targetResourceType));
return(source.EnumerableCast(targetResourceType.InstanceType));
}
/// <summary>
/// Compose SelectMany() to expression
/// </summary>
/// <param name="genericMethodInfo">SelectMany MethodInfo</param>
/// <param name="source">Source expression</param>
/// <param name="selector">Selector expression</param>
/// <returns>Expression with SelectMany()</returns>
private static Expression SelectMany(MethodInfo genericMethodInfo, Expression source, LambdaExpression selector)
{
Debug.Assert(genericMethodInfo != null && genericMethodInfo.IsGenericMethod, "genericMethodInfo != null && genericMethodInfo.IsGenericMethod");
Debug.Assert(source != null, "source != null");
Debug.Assert(selector != null, "selector != null");
Type elementType = source.ElementType();
Debug.Assert(elementType != null, "elementType != null");
Type resultElementType = BaseServiceProvider.GetIEnumerableElement(selector.Body.Type);
MethodInfo selectManyMethod = genericMethodInfo.MakeGenericMethod(elementType, resultElementType);
// Note the ParameterType on an IQueryable mehtod is Expression<Func<>> where as the ParameterType
// on an IEnumerable method is Func<>.
Debug.Assert(
selectManyMethod.GetParameters()[1].ParameterType == selector.GetType() ||
selectManyMethod.GetParameters()[1].ParameterType == selector.Type,
"selector should be of type Expression<Func<TSource, IEnumerable<TResult>>>");
return(Expression.Call(null, selectManyMethod, source, selector));
}
/// <summary>
/// Returns the element type of the expression.
/// </summary>
/// <param name="source">Source expression.</param>
/// <returns>Returns the element type of the expression.</returns>
internal static Type ElementType(this Expression source)
{
Debug.Assert(source != null, "source != null");
return(BaseServiceProvider.GetIEnumerableElement(source.Type) ?? source.Type);
}