[MCP Server]: Unhandled exception. System.DllNotFoundException: Dll was not found.

[Demonese]

Issue Type

Bug

MCP Server Package Version

1.1.12

.NET Version

10.0.100

Environment

• Visual Studio
• VS Code
• GitHub Copilot Coding Agent
• CLI
• Other (please specify below)

If "Other", please specify

Cherry Studio

Prompt or Input

N/A

Expected Response

N/A

Actual Response

Unhandled exception. System.DllNotFoundException: Dll was not found.
   at Microsoft.Build.Locator.NativeMethods.hostfxr_resolve_sdk2(String exe_dir, String working_dir, hostfxr_resolve_sdk2_flags_t flags, hostfxr_resolve_sdk2_result_fn result)
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetSdkFromGlobalSettings(String workingDirectory)
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetDotNetBasePaths(String workingDirectory)+MoveNext()
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetInstances(String workingDirectory, Boolean allowQueryAllRuntimes)+MoveNext()
   at Microsoft.Build.Locator.MSBuildLocator.GetInstances(VisualStudioInstanceQueryOptions options)+MoveNext()
   at System.Linq.Enumerable.TryGetFirstNonIterator[TSource](IEnumerable`1 source, Boolean& found)
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)
   at Microsoft.Build.Locator.MSBuildLocator.RegisterDefaults()
   at NuGet.Mcp.Server.Program.Main(String[] args) in /_/src/NuGet.Mcp.Server/Program.cs:line 27
   at NuGet.Mcp.Server.Program.<Main>(String[] args)

Additional Context or Description

What are the environmental requirements for the MCP service? Have I missed anything?

Application: NuGet.Mcp.Server.exe
CoreCLR Version: 10.0.25.45207
.NET Version: 10.0.0-rc.1.25451.107
Description: The process was terminated due to an unhandled exception.
Exception Info: System.DllNotFoundException: Dll was not found.
   at Microsoft.Build.Locator.NativeMethods.hostfxr_resolve_sdk2(String exe_dir, String working_dir, hostfxr_resolve_sdk2_flags_t flags, hostfxr_resolve_sdk2_result_fn result)
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetSdkFromGlobalSettings(String workingDirectory)
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetDotNetBasePaths(String workingDirectory)+MoveNext()
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetInstances(String workingDirectory, Boolean allowQueryAllRuntimes)+MoveNext()
   at Microsoft.Build.Locator.MSBuildLocator.GetInstances(VisualStudioInstanceQueryOptions options)+MoveNext()
   at System.Linq.Enumerable.TryGetFirstNonIterator[TSource](IEnumerable`1 source, Boolean& found)
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)
   at Microsoft.Build.Locator.MSBuildLocator.RegisterDefaults()
   at NuGet.Mcp.Server.Program.Main(String[] args) in /_/src/NuGet.Mcp.Server/Program.cs:line 27
   at NuGet.Mcp.Server.Program.<Main>(String[] args)

[jebriede]

@Demonese thanks for reaching out about this. Can you please check if dotnet is on your path by opening up a terminal and typing: dotnet --info and let us know. You should get the output from the dotnet command but if you do not, then you'll need to add dotnet to your path. Particularly, dotnet needs to be on the path for Cherry Studio in this case.

[Demonese]

@Demonese thanks for reaching out about this. Can you please check if dotnet is on your path by opening up a terminal and typing: dotnet --info and let us know. You should get the output from the dotnet command but if you do not, then you'll need to add dotnet to your path. Particularly, dotnet needs to be on the path for Cherry Studio in this case.

I tried running it via command in the terminal, but an error still occurs—although the .NET environment is installed.

C:\Windows\System32>dotnet --info
.NET SDK:
 Version:           10.0.100
 Commit:            b0f34d51fc
 Workload version:  10.0.100-manifests.4c0ca8ba
 MSBuild version:   18.0.2+b0f34d51f

运行时环境:
 OS Name:     Windows
 OS Version:  10.0.26200
 OS Platform: Windows
Active code page: 65001

C:\Windows\System32>dotnet --info
.NET SDK:
 Version:           10.0.100
 Commit:            b0f34d51fc
 Workload version:  10.0.100-manifests.4c0ca8ba
 MSBuild version:   18.0.2+b0f34d51f

运行时环境:
 OS Name:     Windows
 OS Version:  10.0.26200
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\10.0.100\

已安装 .NET 工作负载:
没有要显示的已安装工作负载。
已配置为在安装新清单时使用 workload sets。
未安装任何 workload sets。运行 “dotnet workload restore” 以安装工作负载集。

Host:
  Version:      10.0.0
  Architecture: x64
  Commit:       b0f34d51fc

.NET SDKs installed:
  10.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 10.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  None

Environment variables:
  Not set

global.json file:
  Not found

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download

C:\Windows\System32>dnx Nuget.Mcp.Server
Unhandled exception. System.DllNotFoundException: Dll was not found.
   at Microsoft.Build.Locator.NativeMethods.hostfxr_resolve_sdk2(String exe_dir, String working_dir, hostfxr_resolve_sdk2_flags_t flags, hostfxr_resolve_sdk2_result_fn result)
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetSdkFromGlobalSettings(String workingDirectory)
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetDotNetBasePaths(String workingDirectory)+MoveNext()
   at Microsoft.Build.Locator.DotNetSdkLocationHelper.GetInstances(String workingDirectory, Boolean allowQueryAllRuntimes)+MoveNext()
   at Microsoft.Build.Locator.MSBuildLocator.GetInstances(VisualStudioInstanceQueryOptions options)+MoveNext()
   at System.Linq.Enumerable.TryGetFirstNonIterator[TSource](IEnumerable`1 source, Boolean& found)
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)
   at Microsoft.Build.Locator.MSBuildLocator.RegisterDefaults()
   at NuGet.Mcp.Server.Program.Main(String[] args) in /_/src/NuGet.Mcp.Server/Program.cs:line 27
   at NuGet.Mcp.Server.Program.<Main>(String[] args)

[Demonese]

Potentially related issue: dotnet/vscode-csharp#6335

[jebriede]

Thanks for the extra information! I was able to reproduce the issue by simply running dnx NuGet.McpServer on the command line with dotnet on the path and the following SDKs installed:
.NET SDKs installed:
9.0.304 [C:\Program Files\dotnet\sdk]
10.0.100 [C:\Program Files\dotnet\sdk]
10.0.101 [C:\Program Files\dotnet\sdk]