You have to use Unicode which is used by .NET already. For the web page you have to configure the encoding in the web.config
<globalization requestEncoding="utf-8" responseEncoding="utf-8" />
See also How to: Select an Encoding for ASP.NET Web Page Globalization
With MS T-SQL you have to use the nchar and nvarchar (Transact-SQL) | Microsoft Docs
] types to store Unicode text. For other database engines see their documentation.