NET Core 3 Preview 7 AddJsonFile Throws MissingMethodException

System.MissingMethodException HResult=0x80131513 Message=Method not found: ‘System.Text.Json.JsonDocument System.Text.Json.JsonDocument.Parse(System.String, System.Text.Json.JsonReaderOptions)’. Source=Microsoft.Extensions.Configuration.FileExtensions StackTrace: at Microsoft.Extensions.Configuration.FileConfigurationProvider.HandleException(Exception e) at Microsoft.Extensions.Configuration.FileConfigurationProvider.Load(Boolean reload) at Microsoft.Extensions.Configuration.FileConfigurationProvider.Load() at Microsoft.Extensions.Configuration.ConfigurationRoot…ctor(IList`1 providers) at Microsoft.Extensions.Configuration.ConfigurationBuilder.Build()…

To Reproduce

Steps to reproduce the behavior:

1. Using “Microsoft.Extensions.Configuration.Json” Version=“3.0.0-preview7.19362.4”
2. Run this code return new ConfigurationBuilder() .SetBasePath(outputPath) .AddJsonFile(“appsettings.json”, true, true) .AddEnvironmentVariables() .Build();
3. See exception.

Expected behavior

No Exception and Configuration File Loaded and Ready

[dhhunter]

Upon further investigation I realized that the problem was not affecting new projects, only those projects that I had upgraded to Preview 7 from Preview 6. So after beating my head against a wall for a couple of hours today trying to figure out what was going on, I ended up adding a NuGet reference to:

Microsoft.Extensions.Configuration.Json Version=“3.0.0-preview7.19362.4”

In my MS Test Project and it finally worked. It must have been linking against an old version of the assembly that was not showing up in Visual Studio.

Thanks and my sincere apologies for the rushed bug report!

[losdamianos]

I just ran into the exact same issue when I was trying to read appsettings.json on the recently updated project from older preview version .net core to preview 7 after updating Microsoft.Extensions.Configuration.Json to the latest preview everything worked fine