How Can I Cast to Anonymous Types in .NET, and When Should I Avoid Doing So?

Casting to Anonymous Types

In .NET, anonymous types are immutable value types that are generated at compile time. They can be used to represent data that does not warrant the creation of a new class. However, casting to and from anonymous types can be tricky.

One situation where casting to an anonymous type may be necessary is when using it as a data source for data binding in Windows Forms. When trying to cast the Current property of a BindingSource to an anonymous type, an error will occur. This is because the Current property returns an object reference, which cannot be directly cast to an anonymous type.

To overcome this limitation, a trick can be employed to infer the correct type using the compiler. By creating a dummy object of the correct anonymous type and assigning it to the Current value, the compiler can be tricked into inferring the correct type for the cast.

For example:

var a = new { Id = 1, Name = "Bob" };
var b = (typeof(a) as DynamicObject).GetObject();

In this example, the GetObject() method of the DynamicObject class is used to create an instance of the anonymous type. The typeof(a) expression is used to infer the type of the anonymous type.

While this trick can be used to cast to anonymous types, it is generally not recommended to use anonymous types in scenarios where they need to be passed around the program. Instead, it is better to use a real type for improved clarity and maintainability.

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