Regular Expression (Regex) to accept only Alphabets and Space in TextBox in C# and VB.Net

Here Mudassar Khan has explained with an example, how to use Regular Expression (Regex) to accept/allow only Alphabets and Space in TextBox in Windows Forms (WinForms) Applications using C# and VB.Net. When the Validate Button is clicked, the TextBox value will be validated using Regular Expression (Regex) in C# and VB.Net.