You could validate email address using the following ASP.NET code.

C# 8.0 and .NET Core 3.0 – Modern Cross-Platform Development: Build applications with C#, .NET Core, Entity Framework Core, ASP.NET Core, and ML.NET using Visual Studio Code, 4th Edition
ASP.NET Core 3 and Angular 9: Full stack web development with .NET Core 3.1 and Angular 9, 3rd Edition
C# in Depth, 4th Edition

using System.Text.RegularExpressions;

….

// Validate the supplied email address
if( !Regex.Match(Request.Form[“email”],
@”\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*”,
RegexOptions.None).Success)
{
// Invalid email address
}