Create a C# Web API App to fetch NuGet Packages list in Visual Studio

I need to Create a C# Web API Appliation which retreive NuGet Packages list and use it as a Package source in Nuget Package Manager in Visual Studio.

I tried many approaches and i returned the content of "https://api.nuget.org/v3/index.json" as a Json or Xml, etc, but Visual Studio Output shows just this error:

"Data at the root level is invalid. Line 1, position 1."

Do you have any example please?