Custom IComparer in LINQ OrderBy Lambda expression - linq

Question

I have a custom comparer I want to use with OrderBy. I am trying to build a LINQ expression to make it work. So in essence, I am trying to put together an IComparer, OrderBy inLinq expression.
The expression I am trying to build should look something like:
source => source.OrderBy(lambdaParameter => lambdaParameter.Name, new Parsers.NumericComparer()).
With the code below the expression
'{source => source.OrderBy(lambdaParameter => lambdaParameter.Name)}'
is built and I am trying to add this custom Icomparable to this expression
new Parsers.NumericComparer().
This is because I need to do a natural sort. Can someone please help me on how to include this expression. I am trying to read several threads for the past few hours but I have not done understood LINQ expressions well enough yet to implement this. Thanks!
private void CreateOrderByMethod(PropertyDescriptor prop, string orderByMethodName, string cacheKey)
{
/*
Create a generic method implementation for IEnumerable<T>.
Cache it.
*/
var sourceParameter = Expression.Parameter(typeof(List<T>), "source");
var lambdaParameter = Expression.Parameter(typeof(T), "lambdaParameter");
var accesedMember = typeof(T).GetProperty(prop.Name);
var propertySelectorLambda =
Expression.Lambda(Expression.MakeMemberAccess(lambdaParameter, accesedMember), lambdaParameter);
var orderByMethod = typeof(Enumerable).GetMethods()
.Where(a => a.Name == orderByMethodName &&
a.GetParameters().Length == 2)
.Single()
.MakeGenericMethod(typeof(T), prop.PropertyType);
var orderByExpression = Expression.Lambda<Func<List<T>, IEnumerable<T>>>(
Expression.Call(orderByMethod,
new Expression[] { sourceParameter,
propertySelectorLambda }),
sourceParameter);
cachedOrderByExpressions.Add(cacheKey, orderByExpression.Compile());
}

Answer 1

To create an expression that creates a new instance of an object, use Expression.New.
var newParser = Expression.New(typeof(Parsers.NumericComparer));
Then I suggest you use this overload of Expression.Call instead, so that you don't have to go and manually grab the MethodInfo:
var orderByCall = Expression.Call(
typeof(Enumerable),
"OrderBy",
new [] { typeof(T), prop.PropertyType },
sourceParameter, propertySelectorLambda, newParser);