How to solve generic predicate in where clause item?

i face to face 3 errors on where clause" _list.Where (whereClause) " how to solve it?

Error 1
'System.Collections.Generic.List ' does not contain a definition for 'Where' and the best extension method overload 'System.Linq.ParallelEnumerable.Where (System.Linq.ParallelQuery , System.Func )' has some invalid arguments
Error 2 Instance argument: cannot convert from 'System.Collections.Generic.List ' to 'System.Linq.ParallelQuery '
Error 3 Argument 2: cannot convert from 'System.Func ' to 'System.Func '

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace FuncMetodunuTaniyalim3
{
    public class Search<T> where T : class
    {
         private  List<DataModel.Customer> _list;

         public Search()
         {
             _list = new List<DataModel.Customer>();
         }
        public int Find(Func<T, bool> whereClause)
        {
            return _list.IndexOf(_list.Where<T>(whereClause).FirstOrDefault<T>());
        }
    }

    //Repository
    public class DataModel
    {
        private IEnumerable<Customer> customers;

        public List<Customer> Customers
        {
            get { return customers.ToList(); }

        }


        public DataModel()
        {
            customers = new[] { new Customer(){ Id=1, Name="cbfghg", SurName="hfh", Age=29, Dept=0, Income=100},
                                new Customer(){ Id=2, Name="hfghfhf", SurName="erhfghfhfhem", Age=0,Dept=45, Income=300},
                                new Customer(){ Id=3, Name="hgfhgfhf", SurName="balhfghgfhfgh", Age=33, Dept=20, Income=150}};
        }

        //Model
        public class Customer
        {
            public int Id { get; set; }
            public string Name { get; set; }
            public string SurName { get; set; }
            public int Age { get; set; }
            public int Income { get; set; }
            public int Dept { get; set; }

            public Customer()
            {

            }
        }
    }
}

---

Your Search class contains a List<Customer> . Probably you meant to use List<T> :

public class Search<T> where T : class
{
    private List<T> _list;

    public Search()
    {
        _list = new List<T>();
    }
    public int Find(Func<T, bool> whereClause)
    {
        return _list.IndexOf(_list.Where<T>(whereClause).FirstOrDefault<T>());
    }
}

---

Your list is a List<DataModel.Customer> , while your predicate is a Func<T, bool> . Change the type of your predicate to Func<DataModel.Customer, bool> or change your list type to List<T> .

---

你不能这样做，因为List<DataModel.Customer>实现IEnumerable<DataModel.Customer>请看方法文档：http://msdn.microsoft.com/en-us/library/bb534803.aspx也许你想要_list作为List<T>在那里？

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