Updating WebApiClient (#1304)

Adding missing `using` statements

Author: bnookala

docs/csharp/tutorials/console-webapiclient.md

@@ -209,6 +209,8 @@ type to contain the information you use from this response. Let's build this slo
 a simple C# type that contains the name of the repository:
 
 ```cs
+using System;
+
 namespace WebAPIClient
 {
     public class repo
@@ -474,9 +476,17 @@ Let's go over the new constructs above. The `IgnoreDataMember` attribute instruc
 that this type should not be read to or written from any JSON object. This property contains only a
 `get` accessor. There is no `set` accessor. That's how you define a *read only* property in C#. (Yes,
 you can create *write only* properties in C#, but their value is limited.) The `DateTime.ParseExact`
-method parses a string and creates a `DateTime` object to return. If the parse operation fails, the
+method parses a string and creates a `DateTime` object using a provided date format, and adds additional 
+metadata to the `DateTime` using a `CultureInfo` object. If the parse operation fails, the
 property accessor throws an exception.
 
+To use `CultureInfo.InvariantCulture`, you will need to add `System.Globalization` to the using statements 
+in `repo.cs`:
+
+```cs
+using System.Globalization;
+```
+
 Finally, add one more output statement in the console, and you're ready to build and run this app
 again: