In reading C# 4.0 in a Nutshell, I have encountered ways to make one IEnumerable from another of a different type in the midst of a LINQ query. I will give an example that uses these three silly classes:
- namespace Whatever.Models
{
public class Contact
{
public string Name { get; set; }
public string Phone { get; set; }
public string Email { get; set; }
public string Street { get; set; }
public string City { get; set; }
}
}
- namespace Whatever.Models
{
public class Address
{
public string Street { get; set; }
public string City { get; set; }
public string State { get; set; }
}
}
- namespace Whatever.Models
{
public static class StateHelper
{
public static string GetStateForCity(string city)
{
switch (city)
{
case "Globe":
return "Arizona";
case "West Palm Beach":
return "Florida";
case "Santa Cruz":
return "California";
default:
return "Texas";
}
}
}
}
Here is my example. This test passes.
using System.Collections.Generic;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Whatever.Models;
using System.Linq;
namespace Whatever.Tests
{
[TestClass]
public class ContactTests
{
[TestMethod]
public void QueryTest()
{
Contact[] contacts = new Contact[]
{
new Contact()
{
Name = "Johnny",
Phone = "(512) 419-8788",
Email = "pil@example.com",
Street = "500 East Stassney",
City = "Austin"
},
new Contact()
{
Name = "Sid",
Phone = "(928) 425-629",
Email = "fevercheese@gmail.com",
Street = "1 South Broad",
City = "Globe"
},
new Contact()
{
Name = "Steve",
Phone = "(561) 790-0349",
Email = "metal@example.com",
Street = "5055 Club",
City = "West Palm Beach"
},
new Contact()
{
Name = "Paul",
Phone = "(831) 475-8325",
Email = "cook@example.com",
Street = "1515 Ocean",
City = "Santa Cruz"
}
};
IEnumerable<Address> addresses = contacts
.Where(c => c.Email.EndsWith("example.com"))
.OrderBy(c => c.Name)
.Select(c => new Address
{
Street = c.Street,
City = c.City,
State = StateHelper.GetStateForCity(c.City)
});
List<Address> list = addresses.ToList();
Assert.AreEqual(list.Count, 3);
Assert.AreEqual(list[0].Street, "500 East Stassney");
Assert.AreEqual(list[0].City, "Austin");
Assert.AreEqual(list[0].State, "Texas");
Assert.AreEqual(list[1].Street, "1515 Ocean");
Assert.AreEqual(list[1].City, "Santa Cruz");
Assert.AreEqual(list[1].State, "California");
Assert.AreEqual(list[2].Street, "5055 Club");
Assert.AreEqual(list[2].City, "West Palm Beach");
Assert.AreEqual(list[2].State, "Florida");
}
}
}
Here is the same thing with an anonymous type.
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Whatever.Models;
using System.Linq;
namespace Whatever.Tests
{
[TestClass]
public class ContactTests
{
[TestMethod]
public void QueryTest()
{
Contact[] contacts = new Contact[]
{
new Contact()
{
Name = "Johnny",
Phone = "(512) 419-8788",
Email = "pil@example.com",
Street = "500 East Stassney",
City = "Austin"
},
new Contact()
{
Name = "Sid",
Phone = "(928) 425-629",
Email = "fevercheese@gmail.com",
Street = "1 South Broad",
City = "Globe"
},
new Contact()
{
Name = "Steve",
Phone = "(561) 790-0349",
Email = "metal@example.com",
Street = "5055 Club",
City = "West Palm Beach"
},
new Contact()
{
Name = "Paul",
Phone = "(831) 475-8325",
Email = "cook@example.com",
Street = "1515 Ocean",
City = "Santa Cruz"
}
};
var addresses = contacts
.Where(c => c.Email.EndsWith("example.com"))
.OrderBy(c => c.Name)
.Select(c => new
{
Street = c.Street,
City = c.City,
State = StateHelper.GetStateForCity(c.City)
});
Assert.AreEqual(addresses.Count(), 3);
Assert.AreEqual(addresses.ElementAt(0).Street, "500 East Stassney");
Assert.AreEqual(addresses.ElementAt(0).City, "Austin");
Assert.AreEqual(addresses.ElementAt(0).State, "Texas");
Assert.AreEqual(addresses.ElementAt(1).Street, "1515 Ocean");
Assert.AreEqual(addresses.ElementAt(1).City, "Santa Cruz");
Assert.AreEqual(addresses.ElementAt(1).State, "California");
Assert.AreEqual(addresses.ElementAt(2).Street, "5055 Club");
Assert.AreEqual(addresses.ElementAt(2).City, "West Palm Beach");
Assert.AreEqual(addresses.ElementAt(2).State, "Florida");
}
}
}
