dotnet/maui · error · Exception

Error: Couldn't find .cer or .msix file

Error message

Error: Couldn't find .cer or .msix file

What it means

Thrown during packaged-test install when neither the project's AppPackages folder nor the arcade bin fallback (artifacts/bin/<project>/<config>/) contains both a .cer and a .msix file. The build that should have produced the signed MSIX package (with GenerateMsixCert + packaging enabled) did not emit the expected AppPackages output, so sideloading cannot proceed.

Source

Thrown at eng/devices/windows.cake:456

			}
			if(PROJECT.FullPath.Contains("Graphics.DeviceTests"))
			{
				projectDir = MakeAbsolute(new DirectoryPath(arcadeBin + "/Graphics.DeviceTests/" + CONFIGURATION + "/"));
			}
			if(PROJECT.FullPath.Contains("MauiBlazorWebView.DeviceTests"))
			{
				projectDir = MakeAbsolute(new DirectoryPath(arcadeBin + "/MauiBlazorWebView.DeviceTests/" + CONFIGURATION + "/"));
			}	
			if(PROJECT.FullPath.Contains("Essentials.DeviceTests"))
			{
				projectDir = MakeAbsolute(new DirectoryPath(arcadeBin + "/Essentials.DeviceTests/" + CONFIGURATION + "/"));
			}
			cerPaths = GetFiles(projectDir.FullPath + "/**/AppPackages/*/*.cer");
		    msixPaths = GetFiles(projectDir.FullPath + "/**/AppPackages/*/*.msix");
			if(cerPaths.Count() == 0 || msixPaths.Count() == 0)
			{
				Error("Error: Couldn't find .cer or .msix file");
				throw new Exception("Error: Couldn't find .cer or .msix file");
			}
		}

		var msixPath = msixPaths.First();
		var cerPath = cerPaths.First();
		Information($"Found MSIX, installing: {msixPath}");

		int InstallAppxPackage(FilePath path) {
			var absPath = MakeAbsolute(path).FullPath;
			Information("Installing MSIX: {0}", absPath);
			// $ProgressPreference='SilentlyContinue' suppresses Add-AppxPackage's
			// progress output which otherwise chokes cake's stdout pipe.
			return StartProcess("powershell",
				"-NoProfile -Command \"$ProgressPreference='SilentlyContinue'; Add-AppxPackage -Path '" + absPath + "'; if (-not $?) { exit 1 }\"");
		}

		// Install dependencies
		var dependencies = GetFiles(projectDir.FullPath + "/**/AppPackages/**/Dependencies/x64/*.msix");

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Run the build target with MSIX packaging enabled and the same CONFIGURATION as the install step, then confirm AppPackages/<name>_<version>_Test/ contains both .cer and .msix.
2. Ensure GenerateMsixCert ran (packaged runs depend on it) so the package is signed and the .cer is emitted alongside.
3. Verify the project name appears in one of the PROJECT.FullPath.Contains(...) branches; if it is a new project, add a fallback mapping or fix the project dir.
4. Check CONFIGURATION is not empty/Default — an empty config produces a path like artifacts/bin/Controls.DeviceTests// that matches nothing.

Example fix

// before: two lookups then throw with no detail about what was searched
cerPaths = GetFiles(projectDir.FullPath + "/**/AppPackages/*/*.cer");
msixPaths = GetFiles(projectDir.FullPath + "/**/AppPackages/*/*.msix");
if(cerPaths.Count() == 0 || msixPaths.Count() == 0)
    throw new Exception("Error: Couldn't find .cer or .msix file");

// after: report which artifact is missing and where we looked
var cerOk = cerPaths.Count() > 0;
var msixOk = msixPaths.Count() > 0;
if (!cerOk || !msixOk)
    throw new Exception($"Missing {(cerOk ? "" : ".cer ")}{(msixOk ? "" : ".msix ")}under {projectDir}. Build the MSIX package first.");

// After build, assert the AppPackages output exists before install
var cer = GetFiles(projectDir + "/**/AppPackages/*/*.cer");
var msix = GetFiles(projectDir + "/**/AppPackages/*/*.msix");
if (!cer.Any() || !msix.Any())
    throw new Exception($"MSIX/cer missing in {projectDir}. Build with packaging enabled and GenerateMsixCert run.");

When it happens

Trigger: Running the packaged test install without first building the MSIX; building with packaging disabled (no AppPackages dir generated); building into a configuration other than CONFIGURATION so the fallback path is wrong; GenerateMsixCert not run so signing/packaging was skipped; project name not matching any of the Contains() checks so the fallback points nowhere useful.

Common situations: CONFIGURATION mismatch (Debug vs Release) between build and test steps; missing /p:AppxPackage=true or the packaging targets; a clean wiping AppPackages; new DeviceTests project not yet added to the Contains() fallback list; building unpackaged by default.

Related errors

• Cert {certificateThumbprint} exists in LocalMachine\TrustedP
• Failed to install signing cert into LocalMachine\TrustedPeop
• Failed to install app MSIX (exit code {installExit}): {msixP
• ActivateApplication failed (HRESULT=0x{0:X8})
• No test assembly found.

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/3a134f2fb771da45. Report an issue: GitHub.