How To Use C# Linq Predicate with custom Extension Method

Question

I'm trying to write a C# Extension Method, that should take a Predicate and return IQueryable so i can reuse a complicated Where Predicate

Here is what i'm looking at

    public static IEnumerable<T> AddComplexWhere<T>(this IEnumerable<T> query, DBContext context, Func<T, string> PermissionKeyColumn)
    {
        return query.Where(pp => context.Permissions
            .Where(p => /*PermissionKeyColumn is in Permissions Table p.PermissionKey  ??????*/)
            .Where(p => true/* another complicated where*/).Any());
    }

usage will be

context.orders.AddComplexWhere(context,o=>o.permissionKey).ToList()..

this way i can keep reusing the where

Answer 1

To achieve this you need to use

Expression<Func<T, bool>>

Here is example:

public static IEnumerable<T> AddComplexWhere<T>(this IEnumerable<T> query, DBContext context, Expression<Func<T, bool>> expression)
    {
        return query.Where(expression).Any());
    }

After this modification your code should just work:

context.orders.AddComplexWhere(context,o=>o.permissionKey == something).ToList()..