Setting Base Path using ConfigurationBuilder

I was able to solve the issue. If you have not yet solved it, try the following in the project.json. Add the following:

"Microsoft.Extensions.Configuration.FileExtensions": "1.0.0-*",
"Microsoft.Extensions.Configuration.Json": "1.0.0-rc2-final"

and it should work

Not sure if anyone still runs into this issue but I was able to address this in a dotnetcore console project (netcoreapp2.0) via:

dotnet add package Microsoft.Extensions.Configuration.Json

Try adding the following in your .csproj file:

<ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Configuration" Version="2.2.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="2.2.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="2.2.0" />
</ItemGroup>

Something else to consider:

using Microsoft.Extensions.Configuration;

Without that "using" statement, it doesn't find the extension method in Microsoft.Extensions.Configuration.FileExtensions.

The trouble cropped up for me because we were also:

using System.Configuration;

And there was a name clash with "ConfigurationBuilder". Add the

using Microsoft.Extensions.Configuration;

line... remove the

using System.Configuration;

line, then fully qualify anything under System.Configuration.