dotnet/wpf · error · ArgumentException

No file exists at

Error message

No file exists at "{filePath}"

What it means

Verify.FileExists throws ArgumentException when the supplied path is non-empty but File.Exists(filePath) returns false, i.e. no file is present at that path at call time. The message includes the offending path and the exception names the parameter.

Solutions

1. Check File.Exists(path) before calling and correct the path.
2. Use an absolute path built via Path.Combine(AppContext.BaseDirectory, ...) instead of relying on the current working directory.
3. Verify the file was deployed/copied with the application and confirm spelling and extension.

Example fix

// before
theme.Load("res\\Theme.xaml");
// after
string path = Path.Combine(AppContext.BaseDirectory, "res", "Theme.xaml");
if (!File.Exists(path)) throw new FileNotFoundException(path);
theme.Load(path);

string fullPath = Path.GetFullPath(path);
if (!File.Exists(fullPath)) throw new FileNotFoundException($"Missing file: {fullPath}", fullPath);

try { api.Load(path); }
catch (ArgumentException ex) when (ex.Message.StartsWith("No file exists at")) { /* prompt user or fall back to default resource */ }

When it happens

Trigger: Calling a WPF API that calls Verify.FileExists (e.g. resource/font/image loading helpers) with a path to a nonexistent file, or calling Verify.FileExists directly with a stale path.

Common situations: Typo in file name or extension; file deleted or moved after path was computed; relative path resolved against an unexpected working directory; case-sensitivity issues when deploying from Windows to a case-sensitive volume; running without access to a network share makes the file appear missing.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

• SR.FileNotFoundExceptionWithFileName
• ArgumentOutOfRangeException(nameof(offset))
• can’t seek on baseStream
• Cannot open data stream.
• Image_CannotCreateTempFile

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/62e25c2c2b3ebd9e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Standard/Verify.cs:267

        public static void TypeSupportsInterface(Type type, Type interfaceType, string parameterName)
        {
            Assert.IsNeitherNullNorEmpty(parameterName);
            Verify.IsNotNull(type, "type");
            Verify.IsNotNull(interfaceType, "interfaceType");

            if (type.GetInterface(interfaceType.Name) == null)
            {
                throw new ArgumentException("The type of this parameter does not support a required interface", parameterName);
            }
        }
        
        [DebuggerStepThrough]
        public static void FileExists(string filePath, string parameterName)
        {
            Verify.IsNeitherNullNorEmpty(filePath, parameterName);
            if (!File.Exists(filePath))
            {
                throw new ArgumentException($"No file exists at \"{filePath}\"", parameterName);
            }
        }
        
        [DebuggerStepThrough]
        internal static void ImplementsInterface(object parameter, Type interfaceType, string parameterName)
        {
            Assert.IsNotNull(parameter);
            Assert.IsNotNull(interfaceType);
            Assert.IsTrue(interfaceType.IsInterface);

            bool isImplemented = false;
            foreach (var ifaceType in parameter.GetType().GetInterfaces())
            {
                if (ifaceType == interfaceType)
                {
                    isImplemented = true;
                    break;
                }

View on GitHub (pinned to 81131a70a4)