How to create a dynamic LINQ select projection function from a string[] of names?

Question

Using C#...

Is there any way to specify property names for a projection function on a LINQ select method, from an array.

public class          


        

Answer 1

You could use reflection and dynamic types to generate an object with only the specified fields/properties.

Below is a simple way of doing this. You can do optimizations, like having a type cache for the reflection. But this should work for simple fields/properties.

public static object DynamicProjection(object input, IEnumerable properties)
{
    var type = input.GetType();
    dynamic dObject = new ExpandoObject();
    var dDict = dObject as IDictionary;

    foreach (var p in properties)
    {
        var field = type.GetField(p);
        if (field != null)
            dDict [p] = field.GetValue(input);

        var prop = type.GetProperty(p);
        if (prop != null && prop.GetIndexParameters().Length == 0)
            dDict[p] = prop.GetValue(input, null);
    }

    return dObject;
}

Usage:

//...
var names = new[] { "Id", "Name", "Tracks" };
var projection = collection.Select(x => DynamicProjection(x, names));
//...