Convert all classes in the Project or Solution

VB.NET to C# Converter – Instant C#

https://www.tangiblesoftwaresolutions.com/product_details/vb-to-csharp-converter.html

SharpDevelop

https://sourceforge.net/projects/sharpdevelop/files/SharpDevelop%204.x/4.4/SharpDevelop_4.4.2.9749_Setup.msi

Extensions

https://marketplace.visualstudio.com/items?itemName=SharpDevelopTeam.CodeConverter

https://marketplace.visualstudio.com/items?itemName=fishcodelib.ConvertNETBasedonNET45

Tool convert VB.NET to CSharp

https://www.codeproject.com/Articles/310667/NET-Code-Conversion