C#: Difference between using System.Text and System.Text.RegularExpressions

Question

In an ASP.NET C# application, I noticed in order to use Regex and StringBuilder, I had to put both

using System.Text;
using System.Text.RegularExpressions;
         


        

Answer 1

• Regex is defined in System.Text.RegularExpressions
• StringBuilder is defined in System.Text

You need to include both namespaces for these two types to be in scope. Including a namespace A.B doesn't automatically include a contained namespace A.B.C. If this were the case, nested namespaces would be of limited use.