Microsoft.WindowsAppSDK.ML 2.1.70

Using Microsoft.WindowsAppSDK.ML via NuGet

The Microsoft.WindowsAppSDK.ML package brings Windows ML to your project as part of the Windows App SDK. To use it correctly, follow these steps:

Framework-Dependent Deployment (Recommended)

Windows ML is recommended to be used as a framework-dependent component. This means your app should either:

• Reference the main Windows App SDK NuGet package:
  • Add a reference to Microsoft.WindowsAppSDK (recommended). This will automatically include Microsoft.WindowsAppSDK.ML as a transitive dependency.
• Or, reference both ML and WindowsAppSDK Runtime directly:
  • Add references to both Microsoft.WindowsAppSDK.ML and Microsoft.WindowsAppSDK.Runtime.

Note: If you only reference Microsoft.WindowsAppSDK.ML without Microsoft.WindowsAppSDK.Runtime, your app will not deploy or run correctly.

Self-Contained Deployment

For applications that need to bundle ONNX Runtime dependencies locally without relying on framework packages, enable self-contained mode:

<PropertyGroup>
 <WindowsAppSDKSelfContained>true</WindowsAppSDKSelfContained>
</PropertyGroup>

Tip: If ONNX Runtime binaries are not being copied to your output directory correctly, ensure you have an explicit reference to Microsoft.WindowsAppSDK.Base in your project, as this package contains the necessary build targets for binary deployment.

In self-contained mode, ONNX Runtime binaries are deployed alongside your application:

MyApp/
├── MyApp.exe
├── Microsoft.Windows.AI.MachineLearning.dll
├── onnxruntime.dll
└── DirectML.dll

This mode is useful for:

• Applications that cannot depend on framework packages
• Scenarios requiring specific ONNX Runtime versions
• Simplified deployment without framework dependencies

Unpackaged Applications

If your app is unpackaged (not MSIX), add the following property to your project to enable the Windows App SDK bootstrapper:

<WindowsPackageType>None</WindowsPackageType>

This is a temporary requirement and will be auto-detected in future releases.

Execution Provider Enumeration

Windows ML supports enumerating available execution providers through the PackageExtensionCatalog API. However, this functionality has specific requirements and limitations:

Required Capabilities

For execution provider enumeration to work in packaged applications, your app manifest must declare the packageQuery capability:

<Package>
 <Capabilities>
 <uap4:Capability Name="packageQuery" />
 </Capabilities>
</Package>

Execution Provider Enumeration Limitations

• AppContainer Applications: Execution provider enumeration will return empty results if the packageQuery capability is not declared in the app manifest
• LowIL Applications: Execution provider enumeration is not available and will return empty results
• Insufficient Privileges: If the required privileges are not held, execution provider enumeration will return empty results rather than failing.

Unpackaged AppContainer Processes

For unpackaged applications running in AppContainer mode, the packageQuery capability must be granted to the process token when creating the AppContainer. This is done by including the capability SID in the AppContainer creation:

// When creating an AppContainer for an unpackaged process
PSID packageQuerySid = nullptr;
ConvertStringSidToSid(L"S-1-15-3-1024-1962849891-688487262-3571417821-3628679630-802580238-1922556387-206211640-3335523193", &packageQuerySid);

SID_AND_ATTRIBUTES capabilities[] = {
 { packageQuerySid, SE_GROUP_ENABLED }
};

// Include the capabilities when creating the AppContainer token
// This allows the unpackaged AppContainer process to use PackageExtensionCatalog APIs

The SID S-1-15-3-1024-1962849891-688487262-3571417821-3628679630-802580238-1922556387-206211640-3335523193 corresponds to the packageQuery capability.

Fallback Behavior

When execution provider enumeration is not available or returns empty results, Windows ML will gracefully fall back to using built-in providers, e.g. the CPU execution provider.

For applications that require specific execution providers, consider brokering and explicitly configuring them rather than relying on automatic enumeration.

Using ONNX Runtime Headers

The ONNX Runtime headers are included in a winml subdirectory to avoid conflicts with other versions of ONNX Runtime. When using these headers in your code, include them with the subdirectory prefix:

#include <winml/onnxruntime_c_api.h>
#include <winml/onnxruntime_cxx_api.h>

Using ONNX Runtime headers without a prefix

If your existing code uses the headers without the winml/ prefix and you cannot update your includes, you can enable this behavior by setting the WinMLEnableDefaultOrtHeaderIncludePath property in your project:

<PropertyGroup>
 <WinMLEnableDefaultOrtHeaderIncludePath>true</WinMLEnableDefaultOrtHeaderIncludePath>
</PropertyGroup>

Passthrough Mode for Redistributed Components (e.g. dynamic link libraries)

For redistributed components that are consumed by other applications where ONNX Runtime initialization is handled externally, enable passthrough mode:

<PropertyGroup>
 <WindowsAppSDKMLPassthroughOnnxRuntime>true</WindowsAppSDKMLPassthroughOnnxRuntime>
</PropertyGroup>

Passthrough mode is designed for scenarios where:

• Your component is redistributed and consumed by other binaries
• ONNX Runtime is expected to be loaded by the host application (whether framework-dependent, self-contained, or custom initialization)
• The initialization pattern is not known at build time
• You need to provide ONNX Runtime access without managing the runtime lifecycle

In passthrough mode, Windows ML assumes ONNX Runtime (onnxruntime.dll) is already loaded in the current process and uses GetModuleHandle to access the already-loaded library instead of attempting its own initialization or dependency resolution.

Without Windows App SDK

The Microsoft.WindowsAppSDK.ML NuGet package can be referenced without a Windows App SDK dependency (Microsoft.WindowsAppSDK or Microsoft.WindowsAppSDK.Foundation). No additional configuration is required — simply reference Microsoft.WindowsAppSDK.ML on its own.

When used without Windows App SDK, ONNX Runtime headers are available with the winml/ prefix — use #include <winml/onnxruntime_cxx_api.h>. To use headers without the prefix, set WinMLEnableDefaultOrtHeaderIncludePath to true in your project (see Using ONNX Runtime headers without a prefix).

When no Windows App SDK is present, the build targets link onnxruntime.lib and Microsoft.Windows.AI.MachineLearning.lib directly into the consuming binary. This means the OS loader resolves onnxruntime.dll and Microsoft.Windows.AI.MachineLearning.dll at process start using the standard Windows DLL search order, rather than loading it dynamically at runtime. Runtime DLLs (onnxruntime.dll, DirectML.dll, Microsoft.Windows.AI.MachineLearning.dll) are automatically copied from the NuGet package to the output directory at build time when using MSBuild with NuGet targets. For non-MSBuild builds, such as custom or native setups, this automatic copy behavior may not apply.

The C API (WinMLEpCatalog.h, etc.) is also available and provides direct function exports without requiring WinRT class registration.

This is designed for:

• Native C++ applications without a Windows App SDK dependency
• Applications that need a simple xcopy-deployable layout
• Projects using NuGet without Windows App SDK bootstrapping

API Usage

Automatic Initialization

The package implements automatic ONNX Runtime initialization through a custom OrtGetApiBase implementation. This takes care of the initialization details and provides transparent access to the ONNX Runtime binaries shipping with Windows ML without requiring developers to link against onnxruntime.lib. See include\WindowsMLAutoInitializer.cpp.

Manual Initialization Control

For applications requiring explicit control over initialization sequences or those not utilizing ONNX Runtime APIs, auto-initialization can be disabled via MSBuild property:

<PropertyGroup>
 
 <DisableWindowsAppSDKMLAutoInitialize>true</DisableWindowsAppSDKMLAutoInitialize>
</PropertyGroup>

Native ONNX Runtime Linking (Advanced/Edge-Case Scenario)

For advanced C++ applications where the auto-initializer pattern is not feasible and you need to directly link against the ONNX Runtime import library, you can enable native linking:

<PropertyGroup>
 <WindowsMLNativeLinkOnnxRuntime>true</WindowsMLNativeLinkOnnxRuntime>
</PropertyGroup>

⚠️ Important: This is an edge-case scenario for advanced users. Most applications should use the standard auto-initialization approach described above.

When WindowsMLNativeLinkOnnxRuntime is set to true:

• Auto-initialization is automatically disabled - no need to set DisableWindowsAppSDKMLAutoInitialize
• Platform-specific import library is linked - automatically selects the correct onnxruntime.lib for your target platform (x64, ARM64, ARM64EC)
• ONNX Runtime headers are available - use #include <winml/onnxruntime_c_api.h> or #include <winml/onnxruntime_cxx_api.h>

Critical Dependency Requirements

The consuming binary must ensure the correct onnxruntime.dll is available in the proper search order:

1. For packaged applications: Explicitly reference the Windows App SDK framework package to ensure ONNX Runtime DLLs are available in the package
2. For unpackaged applications: Carefully manage DLL search order to ensure the correct ONNX Runtime version is loaded first
3. Self-contained deployment: Ensure ONNX Runtime DLLs are deployed alongside your application

Failure to meet these requirements will result in runtime linking errors or incompatible DLL loading.

This mode is only recommended for:

• Applications with complex initialization sequences that cannot use auto-initialization
• Custom ONNX Runtime integration scenarios requiring precise lifecycle control
• Edge cases where the standard auto-initializer pattern conflicts with application architecture

Build and Run

Build your project as usual. The Windows ML APIs will be available for use.

More Information

• See the main Windows ML documentation for API usage.
• For more on Windows App SDK, see the WindowsAppSDK docs.
• For more on framework-dependent deployment see WindowsAppSDK deployment
• For sample projects, check the Samples directory or visit WindowsAppSDK-Samples.