Added new section (#26554)

* Added new section

Added a new section for defining what can be returned in custom methods and how to correct a mistake with returns

* Update guide/english/csharp/return/index.md

Co-Authored-By: marcusparsons <marcusparsons@users.noreply.github.com>

* Update guide/english/csharp/return/index.md

Co-Authored-By: marcusparsons <marcusparsons@users.noreply.github.com>

* Update guide/english/csharp/return/index.md

Co-Authored-By: marcusparsons <marcusparsons@users.noreply.github.com>

* Update guide/english/csharp/return/index.md

Co-Authored-By: marcusparsons <marcusparsons@users.noreply.github.com>

guide/english/csharp/return/index.md

@@ -33,6 +33,44 @@ class Calc
 ```
 
 ## Output:
-```
+```csharp
 > The sum of 4 and 3 is 7
 ```
+
+## What Can Be Returned?
+It's important to realize what can be returned in a method.  The type you return must match the type you initialize with the method you're calling.  
+
+Let's take a look at an example which **does not work**:
+
+```csharp
+public static void Main (string[] args) {
+	var answer = Sum(1, 3);
+	Console.WriteLine(answer);
+}
+
+public int Sum(int a, int b) {
+    return "Your sum is: " + (a + b);
+}
+```
+
+If you copy and paste the above code into a C# compiler and attempt to run it, you will get an error about not being able to convert `string` to `int`. The reason why is that we are saying with `public int Sum` and that we are guaranteeing to `return` an `int` and in our `return` statement, we are returning a `string` because all primitive types (`int`, `double`, `float`, `boolean`, etc.) are converted to a `string` when concatenated (the `+` sign)  with a `string` type.
+
+In this case, to correct this mistake, we either need to change this `Sum` function to `return` a `string` or keep it as an `int` type and handle the flavor text of the answer outside of the method.  I'm going to go with the latter, and handle this as an `int` return type and add in that text "Your sum is: " to the calling method.
+
+
+```csharp
+public static void Main (string[] args) {
+	var answer = Sum(1, 3);
+	Console.WriteLine("Your sum is: " + answer);
+}
+
+public int Sum(int a, int b) {
+    return a + b;
+}
+```
+
+After running the above program, the code executes and outputs:
+
+```text
+Your sum is: 4
+```