dotnet/BenchmarkDotNet · error · NotSupportedException

Found more than one matching project file for {projectName}

Error message

Found more than one matching project file for {projectName} in {rootDirectory.FullName} and its subfolders: '{files[0].FullName}','{files[1].FullName}'. Benchmark project names needs to be unique.

What it means

CsProjGenerator requires benchmark project names to be unique under rootDirectory; finding two or more project files with the same name is ambiguous and aborts the build.

Source

Thrown at src/BenchmarkDotNet/Toolchains/CsProj/CsProjGenerator.cs:437

            || directory.Name.StartsWith(".", StringComparison.Ordinal)
#if NETSTANDARD2_0
            || directory.Attributes.HasFlag(FileAttributes.Hidden)
            || directory.Attributes.HasFlag(FileAttributes.ReparsePoint)
#endif
            ;

        public static FileInfo FindProjectFile(DirectoryInfo rootDirectory, string projectName)
        {
            var projectFiles = EnumerateProjectFiles(rootDirectory, projectName);

            // Take first 2 items for performance reasons
            var files = projectFiles.Take(2).ToArray();
            return files.Length switch
            {
                1 => files[0],
                0 => throw new NotSupportedException(
                    $"Unable to find {projectName} in {rootDirectory.FullName} and its subfolders. Most probably the name of output exe is different than the name of the .(c/f)sproj"),
                _ => throw new NotSupportedException(
                    $"Found more than one matching project file for {projectName} in {rootDirectory.FullName} and its subfolders: '{files[0].FullName}','{files[1].FullName}'. Benchmark project names needs to be unique."),
            };
        }

        private static IEnumerable<FileInfo> EnumerateProjectFiles(DirectoryInfo rootDirectory, string projectName)
        {
            var stack = new Stack<DirectoryInfo>();
            stack.Push(rootDirectory);

            while (stack.Count > 0)
            {
                var currentDir = stack.Pop();

                // 1. Search '*.proj' files in the current directory
                IEnumerable<FileInfo> files = EnumerateProjectFiles(currentDir);

                foreach (var file in files)
                {

View on GitHub (pinned to b515068b61)

Solutions

1. Rename one of the duplicate projects so every benchmark project name is unique within the search tree.
2. Narrow the rootDirectory so only one matching project file is found.
3. Remove stale copies of the project (e.g. backup folders) from the subfolders being searched.

When it happens

Trigger: Thrown at src/BenchmarkDotNet/Toolchains/CsProj/CsProjGenerator.cs:437 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of dotnet/BenchmarkDotNet@b515068b61 (2026-08-13). Data as JSON: /api/errors/a2f8a7ccfef8aecc. Report an issue: GitHub.