Rule Definition
A string representation of a URI is prone to parsing and encoding errors and can lead to security vulnerabilities. The Uri class provides these services in a safe and secure manner. When there is a choice between two overloads that differ only regarding the representation of a URI, the user should choose the overload that takes a Uri argument.

Remediation
To fix a violation of this rule, call the overload that takes the Uri argument.

Violation Code Sample

using System;

namespace DesignLibrary
{
   class History
   {
      internal void AddToHistory(string uriString) {}
      internal void AddToHistory(Uri uriType) {}
   }

public class Browser
   {
      History uriHistory = new History();

      public void ErrorProne()
      {
         uriHistory.AddToHistory("http://www.adventure-works.com");
      }
   }
}

Fixed Code Sample

using System;

namespace DesignLibrary
{
   class History
   {
      internal void AddToHistory(string uriString) {}
      internal void AddToHistory(Uri uriType) {}
   }


public class Browser
   {
      History uriHistory = new History();

public void SaferWay()
      {
         try
         {
            Uri newUri = new Uri("http://www.adventure-works.com");
            uriHistory.AddToHistory(newUri);
         }
         catch(UriFormatException uriException) {}
      }
    }

https://docs.microsoft.com/en-us/visualstudio/code-quality/ca2234?view=vs-2019