The Rename allows you to rename a parameter:
DelFunc.DF1 add = (int a, int b) => a + b; var add2 = add.Rename(a_x: 0); var onePlusTwo = add2.Invoke(x: 1, b: 2);
DelFunc.DF1 is a Delegate Function. Delegate Functions is a way to support treating lambdas as functions.
In the above example, the function returned by Rename has two parameters: x and b instead of a and b.