How Can I Cast an Object to an Anonymous Type in C#?

Cast to Anonymous Type

The question is how to cast an object to an anonymous type. Anonymous types are created using object initializers and are often used as a convenient way to store data. However, they do not have a type name, which can make it difficult to cast them.

One way to cast an object to an anonymous type is to use a trick that involves using a dummy value of the desired anonymous type. This dummy value is used to infer the type of the object to be cast. Here is an example:

public class Program
{
    public static void Main(string[] args)
    {
        var a = new { Id = 1, Name = "Bob" };
        TestMethod(a);
    }

    private static void TestMethod(object x)
    {
        // This is a dummy value, just to get 'a' to be of the right type
        var a = new { Id = 0, Name = "" };
        a = Cast(a, x);
        Console.WriteLine(a.Id + ": " + a.Name);
    }

    private static T Cast<T>(T typeHolder, object x)
    {
        // typeHolder above is just for compiler magic
        // to infer the type to cast x to
        return (T)x;
    }
}

Another way to cast an object to an anonymous type is to use a generic extension method. This method can be used to cast an object to any anonymous type. Here is an example:

public static class AnonymousTypeExtensions
{
    public static T CastTo<T>(this object value, T targetType)
    {
        // targetType above is just for compiler magic
        // to infer the type to cast value to
        return (T)value;
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        var a = new { Id = 1, Name = "Bob" };
        var b = a.CastTo(new { Id = 0, Name = "" });
        Console.WriteLine(b.Id + ": " + b.Name);
    }
}

However, it is important to note that using anonymous types in this way can be tricky and is not recommended in general. It is better to use a real type instead.

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