private static MethodCallExpression Apply(string methodName, Expression source, Expression argument = null)
{
var result = Expression.Call(
type: typeof(Queryable),
methodName: methodName,
typeArguments: methodName == "Select" || methodName.StartsWith("OrderBy", StringComparison.Ordinal)
? source.Type.GetGenericArguments(typeof(IQueryable <>))
.Concat(new[] { ((LambdaExpression)LinqHelpers.UnQuote(argument)).ReturnType })
.ToArray()
: source.Type.GetGenericArguments(typeof(IQueryable <>)),
arguments: argument != null
? new[] { source, argument }
: new[] { source }
);
return(result);
}
