C# Type comparison using reflection

Question

I'd like to check if a property is of type DbSet<T> using reflection.

public class Foo
{
    public DbSet<Bar> Bars { get; set; }
}

By using reflection:

var types = Assembly.GetExecutingAssembly().GetTypes();
foreach (var type in types)
{
    if (type.IsSubclassOf(typeof (Foo)) || type.FullName == typeof (Foo).FullName)
    {
        foreach (
            var prop in Type.GetType(type.FullName).
                GetProperties(BindingFlags.Public | BindingFlags.DeclaredOnly | BindingFlags.Instance))
        {
            var propType = prop.PropertyType;
            bool a = propType.IsAssignableFrom(typeof (DbSet<>));
            bool b = typeof (DbSet<>).IsAssignableFrom(propType);

            bool c = propType.BaseType.IsAssignableFrom(typeof (DbSet<>));
            bool d = typeof (DbSet<>).IsAssignableFrom(propType.BaseType);


            bool e = typeof (DbSet<>).IsSubclassOf(propType);
            bool f = typeof (DbSet<>).IsSubclassOf(propType.BaseType);
            bool g = propType.IsSubclassOf(typeof (DbSet<>));
            bool h = propType.BaseType.IsSubclassOf(typeof (DbSet<>));

            bool i = propType.BaseType.Equals(typeof (DbSet<>));
            bool j = typeof (DbSet<>).Equals(propType.BaseType);

            bool k = propType.Name == typeof (DbSet<>).Name;
        }
    }
}

• Is there a merged solution to check the type? As you can see, I'm using IsSubClassOf + FullName to get classes of type Foo and any other class which is derived from Foo .

• all the checks (a to j) except c,f,k return false. c,f return System.Object as BaseType which is no use for me. k, I consider an unsafe check . But will be my what I use if no other workaround is found. In debug mode, the propType 's FullName is:

   System.Data.Entity.DbSet`1[[Console1.Bar, ConsoleApplication1, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] 

  Is there any other way to check if propType is of type DbSet<> ?
  Thanks.

Answer 1

Do you need it to cope with subclasses of DbSet<> as well? If not, you can use:

if (propType.IsGenericType &&
    propType.GetGenericTypeDefinition() == typeof(DbSet<>))

Full sample:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

class Test<T>
{
    public List<int> ListInt32 { get; set; }
    public List<T> ListT { get; set; }
    public string Other { get; set; }
    public Action<string> OtherGeneric { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        var query = from prop in typeof(Test<string>).GetProperties()
                    let propType = prop.PropertyType
                    where propType.IsGenericType &&
                          propType.GetGenericTypeDefinition() == typeof(List<>)
                    select prop.Name;

        foreach (string name in query)
        {
            Console.WriteLine(name);
        }
    }
}

With subclasses you'd just need to apply the same test recursively up the inheritance hierarchy. It becomes more of a pain if you need to test for interfaces.

Answer 2

The problem with your code is that it is assuming that typeof(DbType<>) denotes a regular type. It is not a normal type: rather, it is a generic type definition. That is why the IsAssignableFrom , IsSubclassOf etc. are not going to work. Type x is of type DbSet<T> if the following condition is true:

x.IsGenericType && x.GetGenericTypeDefinition() == typeof(DbSet<>) && x.GetGenericTypeArguments()[0] == typeof(T)

Answer 3

I'd suggest the following type comparision (worked fine for me):

foreach (var prop in customObject.GetType().GetProperties().Where(e => e.CanRead && e.CanWrite))
{
    var typeName = prop.PropertyType.FullName ?? "";
    //!!! Type comparision here:
    if (typeName == typeof(string).FullName)
    {
        prop.SetValue(customObject, "abc");
        continue;
    }
    // other code
}

For nullable types (for example DateTime? ) you might use this type of comparison:

if (typeName.Contains(typeof(string).FullName))
{
    prop.SetValue(customObject, "abc");
}