Add guideline for building nuget package and example usage

csharp/.gitignore

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+/.vs/
+/local_feed/
+/Microsoft.ML.OnnxRuntime.EP.TensorRT/runtimes/**/native/*.dll
+*.nupkg
+*.snupkg
+**/packages/*
+!**/packages/build/
+**/bin/*

csharp/Microsoft.ML.OnnxRuntime.EP.TensorRT/Microsoft.ML.OnnxRuntime.EP.TensorRT.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+
+    <Runtime Condition=" $([MSBuild]::IsOsPlatform('Windows')) AND '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'X64' ">win-x64</Runtime>
+    <Runtime Condition=" $([MSBuild]::IsOsPlatform('Windows')) AND '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'Arm64' ">win-arm64</Runtime>
+
+    <!-- Package info -->
+    <PackageId>Microsoft.ML.OnnxRuntime.EP.TensorRT</PackageId>
+    <Version>1.0.0</Version>
+    <Authors>ORT</Authors>
+    <Company>Microsoft</Company>
+    <Description>A package for a TensorRT plugin EP.</Description>
+    <PackageReadmeFile>readme.md</PackageReadmeFile>
+
+    <!-- License/Repository -->
+    <PackageLicenseExpression>MIT</PackageLicenseExpression>
+    <RepositoryUrl>https://github.com/microsoft/onnxruntime-inference-examples</RepositoryUrl>
+    <RepositoryType>git</RepositoryType>
+
+    <!-- Include symbols/source for better debugging experience -->
+    <IncludeSymbols>true</IncludeSymbols>
+    <SymbolPackageFormat>snupkg</SymbolPackageFormat>
+
+    <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- Ensure README is included in the package -->
+    <None Include="readme.md" Pack="true" PackagePath="" />
+  </ItemGroup>
+
+  <!-- Copy EP DLL to output directory under runtimes/*/native/ -->
+  <ItemGroup Condition="'$(Runtime)' == 'win-x64'">
+    <None Include="runtimes\win-x64\native\tensorrt_plugin_ep.dll"
+          Pack="true"
+          PackagePath="runtimes/win-x64/native/tensorrt_plugin_ep.dll"
+          CopyToOutputDirectory="PreserveNewest"/>
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(Runtime)' == 'win-arm64'">
+    <None Include="runtimes\win-arm64\native\tensorrt_plugin_ep.dll"
+          Pack="true"
+          PackagePath="runtimes/win-arm64/native/tensorrt_plugin_ep.dll"
+          CopyToOutputDirectory="PreserveNewest"/>
+  </ItemGroup>
+
+</Project>

csharp/Microsoft.ML.OnnxRuntime.EP.TensorRT/TensorRTEp.cs

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+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.ML.OnnxRuntime.EP.TensorRT;
+
+public static class TensorRTEp
+{
+    /// <summary>
+    /// Returns the path to the plugin EP library DLL contained by this package.
+    /// Can be passed to OrtEnv::RegisterExecutionProviderLibrary().
+    ///
+    /// Note: It is recommended that plugin EP packages provide this information to applications.
+    /// </summary>
+    /// <returns>EP library path</returns>
+    /// <exception cref="FileNotFoundException">If the EP DLL file path does not exist</exception>
+    public static string GetLibraryPath()
+    {
+        string rootDir = GetNativeDirectory();
+        string osArch = $"{GetOSTag()}-{GetArchTag()}";
+        string epDllPath = Path.GetFullPath(Path.Combine(rootDir, "runtimes", osArch,
+                                                         "native", "tensorrt_plugin_ep.dll"));
+
+        if (!File.Exists(epDllPath))
+        {
+            // This indicates a packaging error.
+            throw new FileNotFoundException($"Did not find EP DLL file: {epDllPath}");
+        }
+
+        return epDllPath;
+    }
+
+    /// <summary>
+    /// Returns the names of the EPs created by the plugin EP library.
+    /// Can be used to select a OrtEpDevice from those returned by OrtEnv::GetEpDevices().
+    ///
+    /// Note: It is recommended that plugin EP packages provide this information to applications.
+    /// </summary>
+    /// <returns>Array of EP names</returns>
+    public static string[] GetEpNames()
+    {
+        return ["TensorRTPluginExecutionProvider"];
+    }
+
+    /// <summary>
+    /// Returns the name of the one EP supported by this plugin EP library.
+    ///
+    /// Note: This is a convenience function exposed by plugin EP packages that only have one EP name.
+    /// </summary>
+    /// <returns></returns>
+    public static string GetEpName()
+    {
+        return GetEpNames()[0];
+    }
+
+    private static string GetNativeDirectory()
+    {
+        var assemblyDir = Path.GetDirectoryName(typeof(TensorRTEp).Assembly.Location);
+
+        // Try returning where this assembly lives (works for framework-dependent)
+        if (!string.IsNullOrEmpty(assemblyDir) && Directory.Exists(assemblyDir))
+            return assemblyDir;
+
+        // Fallback to AppContext.BaseDirectory (works for single-file/self-contained)
+        return AppContext.BaseDirectory;
+    }
+
+    private static string GetOSTag()
+    {
+        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return "win";
+        if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux)) return "linux";
+        return "unknown";
+    }
+
+    private static string GetArchTag()
+    {
+        return RuntimeInformation.OSArchitecture switch
+        {
+            Architecture.X64 => "x64",
+            Architecture.Arm64 => "arm64",
+            _ => "unknown"
+        };
+    }
+}

csharp/SampleApp/Program.cs

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+using System;
+using System.Collections.Generic;
+using System.IO;
+
+using Microsoft.ML.OnnxRuntime.EP.TensorRT;
+using Microsoft.ML.OnnxRuntime;
+
+class Program
+{
+    static void Main()
+    {
+        string epLibPath = TensorRTEp.GetLibraryPath();
+        string epName = TensorRTEp.GetEpName();
+        string epRegistrationName = epName;
+
+        var env = OrtEnv.Instance();
+        env.RegisterExecutionProviderLibrary(epRegistrationName, epLibPath);
+        Console.WriteLine($"Registered EP library: {epLibPath}");
+
+        try
+        {
+            // Find the OrtEpDevice for the EP
+            OrtEpDevice? epDevice = null;
+            foreach (var d in env.GetEpDevices())
+            {
+                if (string.Equals(epName, d.EpName, StringComparison.OrdinalIgnoreCase))
+                {
+                    epDevice = d;
+                }
+            }
+
+            if (epDevice == null)
+            {
+                Console.Error.WriteLine($"ERROR: Unable to find OrtEpDevice with name {epName}");
+                return;
+            }
+            Console.WriteLine($"Found OrtEpDevice for EP: {epName}");
+
+            // Create session with EP
+            using var sessionOptions = new SessionOptions();
+            sessionOptions.AppendExecutionProvider(env, [epDevice], new Dictionary<string, string> { });
+            sessionOptions.AddSessionConfigEntry("session.disable_cpu_ep_fallback", "1");  // Don't run on CPU EP
+
+            string inputModelPath = Path.Combine(AppContext.BaseDirectory, "mul.onnx");
+            Console.WriteLine($"Loading model: {inputModelPath}");
+
+            using var session = new InferenceSession(inputModelPath, sessionOptions);
+
+            // Run model
+            float[] inputData = [1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f];
+            using var inputOrtValue = OrtValue.CreateTensorValueFromMemory<float>(inputData, [2, 3]);
+            var inputValues = new List<OrtValue> { inputOrtValue, inputOrtValue }.AsReadOnly();
+            var inputNames = new List<string> { "x", "y" }.AsReadOnly();
+            using var runOptions = new RunOptions();
+
+            using var outputs = session.Run(runOptions, inputNames, inputValues, session.OutputNames);
+
+            Console.WriteLine($"Input: {string.Join(", ", inputData)}");
+            Console.WriteLine($"Output: {string.Join(", ", outputs[0].GetTensorDataAsSpan<float>().ToArray())}");
+        }
+        finally
+        {
+            env.UnregisterExecutionProviderLibrary(epRegistrationName);
+        }
+    }
+}

csharp/SampleApp/SampleApp.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.ML.OnnxRuntime.EP.TensorRT" Version="1.0.0" />
+    <PackageReference Include="Microsoft.ML.OnnxRuntime" Version="1.24.1" />
+  </ItemGroup>
+
+  <ItemGroup>
+      <Content Include="mul.onnx">
+          <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      </Content>
+  </ItemGroup>
+
+  <!-- Consume nuget package via project reference during development to get live code changes -->
+  <!-- <ItemGroup>
+    <ProjectReference Include="..\Microsoft.ML.OnnxRuntime.EP.TensorRT\Microsoft.ML.OnnxRuntime.EP.TensorRT.csproj" />
+  </ItemGroup> -->
+
+</Project>

csharp/nuget.config

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+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <add key="local_feed" value="./local_feed" />
+  </packageSources>
+</configuration>

csharp/readme.md

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+# TensorRT Plugin Execution Provider with C#
+
+## Contents
+- `Microsoft.ML.OnnxRuntime.EP.TensorRT/`: Contains files for the TensorRT plugin EP C# NuGet package. `TensorRTEp.cs` provides helper functions to get the EP library path and the EP name.
+- `SampleApp/`: Contains a sample C# application showing example usage of the TensorRT plugin EP C# NuGet package.
+- `setup.bat`: Batch script to generate the NuGet package.
+
+## Build Instructions
+This example currently only supports Windows x64 and Windows ARM64.
+
+### Build the native plugin EP library
+
+Follow instructions [here](../README.md#build-instructions) to build the native library.
+
+### Build the C\# NuGet Package
+
+Set the environment variable `TENSORRT_PLUGIN_EP_LIBRARY_PATH` to the path to the native plugin EP shared library. E.g., `tensorrt_plugin_ep.dll`.
+
+Run `setup.bat` from this directory. Pass the build configuration (e.g., Release or Debug) as an argument.
+
+```
+.\setup.bat Release
+```
+
+The generated NuGet package will be copied to the `./local_feed` directory.
+
+## Build and run the sample application
+
+Build and run the sample application.
+
+```
+dotnet build .\SampleApp\SampleApp.csproj -c Release
+dotnet run --project .\SampleApp\SampleApp.csproj -c Release
+```

csharp/setup.bat

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+@echo off
+
+REM Builds NuGet package that wraps TensorRT plugin EP
+
+IF "%~1"=="" (
+    echo ERROR: No build configuration specified.
+    echo Usage: .\setup.bat [Debug^|Release]
+    exit /b 1
+)
+
+SET "BUILD_CONFIG=%~1"
+
+if "%TENSORRT_PLUGIN_EP_LIBRARY_PATH%"=="" (
+    echo ERROR: TENSORRT_PLUGIN_EP_LIBRARY_PATH environment variable is not set.
+    exit /b 1
+)
+
+if not exist "%TENSORRT_PLUGIN_EP_LIBRARY_PATH%" (
+    echo ERROR: EP library "%TENSORRT_PLUGIN_EP_LIBRARY_PATH%" not found.
+    exit /b 1
+)
+
+set "ARCH=%PROCESSOR_ARCHITECTURE%"
+if defined PROCESSOR_ARCHITEW6432 set "ARCH=%PROCESSOR_ARCHITEW6432%"
+
+if /i "%ARCH%"=="AMD64" (
+    set "DEST_EP_DLL_FOLDER=.\Microsoft.ML.OnnxRuntime.EP.TensorRT\runtimes\win-x64\native\"
+) else if /i "%ARCH%"=="ARM64" (
+    set "DEST_EP_DLL_FOLDER=.\Microsoft.ML.OnnxRuntime.EP.TensorRT\runtimes\win-arm64\native\"
+) else (
+    echo ERROR: Unknown architecture "%ARCH%"
+    exit /b 1
+)
+
+if not exist "%DEST_EP_DLL_FOLDER%" (
+    mkdir "%DEST_EP_DLL_FOLDER%" || (
+        echo ERROR: Failed to create "%DEST_EP_DLL_FOLDER%".
+        exit /b 1
+    )
+)
+
+echo Copying EP DLL to "%DEST_EP_DLL_FOLDER%"
+copy /Y "%TENSORRT_PLUGIN_EP_LIBRARY_PATH%" "%DEST_EP_DLL_FOLDER%" >nul
+
+if errorlevel 1 (
+    echo ERROR: Failed to copy EP library to "%DEST_EP_DLL_FOLDER%".
+    exit /b 1
+)
+
+echo Building NuGet package ("%BUILD_CONFIG%") ...
+dotnet build .\Microsoft.ML.OnnxRuntime.EP.TensorRT\Microsoft.ML.OnnxRuntime.EP.TensorRT.csproj -c "%BUILD_CONFIG%"
+dotnet pack .\Microsoft.ML.OnnxRuntime.EP.TensorRT\Microsoft.ML.OnnxRuntime.EP.TensorRT.csproj -c "%BUILD_CONFIG%"
+
+set "LOCAL_FEED_FOLDER=local_feed"
+if not exist "%LOCAL_FEED_FOLDER%" (
+    mkdir "%LOCAL_FEED_FOLDER%" || (
+        echo ERROR: Failed to create "%LOCAL_FEED_FOLDER%"
+        exit /b 1
+    )
+)
+
+copy /Y .\Microsoft.ML.OnnxRuntime.EP.TensorRT\bin\"%BUILD_CONFIG%"\Microsoft.ML.OnnxRuntime.EP.TensorRT.*.nupkg .\local_feed\
+copy /Y .\Microsoft.ML.OnnxRuntime.EP.TensorRT\bin\"%BUILD_CONFIG%"\Microsoft.ML.OnnxRuntime.EP.TensorRT.*.snupkg .\local_feed\