使用Activator:

//
// Summary: 
// Creates an instance of the specified type using that type's default constructor. 
// 
// Parameters: 
// type: 
// The type of object to create. 
// 
// nonPublic: 
// true if a public or nonpublic default constructor can match; false if only 
// a public default constructor can match. 
// 
// Returns: 
// A reference to the newly created object. 
public static object CreateInstance(Type type, bool nonPublic);
 

例項：

public class Singleton<T> where T : class
{
	private static T singleton;
	public static T Instance
	{
		get
		{
			if (Singleton<T>.singleton == default(T))
			{
				try
				{
					Singleton<T>.singleton = (T)Activator.CreateInstance(typeof(T), true);
				}
				catch (TargetInvocationException ex)
				{
					throw ex.InnerException;
				}
			}
			return Singleton<T>.singleton;
		}
	}
}