Microsoft .NET 6 SDK empowers C# developers to build cross-platform DotNet applications for Windows, Linux, and macOS from one codebase. This article describes the steps to build a .NET 6 barcode and QR code decoding library based on Dynamsoft C/C++ Barcode SDK, as well as how to pack the library into a NuGet package.

.NET 6 SDK Installation

• Windows
• Linux
• Mac

Dynamsoft Barcode Reader

1. Download C/C++ SDK v9.0.
2. Get a valid license key for activating the SDK.

Steps to Develop and Build .NET 6 Barcode and QR Code SDK

1. Create a new library project:
   

   dotnet new classlib -o BarcodeQRCodeSDK
   

2. Copy shared library files from the C/C++ SDK package to the project root directory. For different platforms, the minimum required shared library files are:

- Windows: `DynamsoftBarcodeReader.dll`, `vcomp110.dll`
- Linux: `libDynamsoftBarcodeReader.so`
- macOS: `libDynamsoftBarcodeReader.dylib`    

1. Rename Class1.cs to BarcodeQRCodeReader.cs.

2. P/Invoke is the technology used for bridging C/C++ and .NET. In the BarcodeQRCodeReader.cs file, we use DllImport to load the unmanaged shared library (e.g. *.dll, *.so, *.dylib) and define some managed methods to communicate with the native component.
   

   [DllImport("DynamsoftBarcodeReader")]
   static extern IntPtr DBR_CreateInstance();
   
   [DllImport("DynamsoftBarcodeReader")]
   static extern void DBR_DestroyInstance(IntPtr hBarcode);
   
   [DllImport("DynamsoftBarcodeReader")]
   static extern int DBR_InitLicense(string license, [Out] byte[] errorMsg, int errorMsgSize);
   
   [DllImport("DynamsoftBarcodeReader")]
   static extern int DBR_DecodeFile(IntPtr hBarcode, string filename, string template);
   
   [DllImport("DynamsoftBarcodeReader")]
   static extern int DBR_FreeTextResults(ref IntPtr pTextResultArray);
   
   [DllImport("DynamsoftBarcodeReader")]
   static extern void DBR_GetAllTextResults(IntPtr hBarcode, ref IntPtr pTextResultArray);
   
   [DllImport("DynamsoftBarcodeReader")]
   static extern int DBR_DecodeBuffer(IntPtr hBarcode, IntPtr pBufferBytes, int width, int height, int stride, ImagePixelFormat format, string template);
   
   [DllImport("DynamsoftBarcodeReader")]
   static extern int DBR_DecodeBase64String(IntPtr hBarcode, string base64string, string template);
   

3. In addition, we need to define some native structs in C#:
   

   [StructLayout(LayoutKind.Sequential, Pack = 1)]
   internal struct PTextResult
   {
       BarcodeFormat emBarcodeFormat;
       public string barcodeFormatString;
       BarcodeFormat_2 barcodeFormat_2;
       string barcodeFormatString_2;
       public string barcodeText;
       IntPtr barcodeBytes;
       int barcodeBytesLength;
       IntPtr localizationResult;
       IntPtr detailedResult;
       int resultsCount;
       IntPtr results;
       [MarshalAs(UnmanagedType.ByValArray, SizeConst = 56)]
       char[] reserved;
   }
   
   [StructLayout(LayoutKind.Sequential, Pack = 1)]
   internal struct TextResultArray
   {
       public int resultsCount;
       public IntPtr results;
   }
   

4. The memory operation between the managed structure and the unmanaged pointer is a little bit tricky. We need to use Marshal to convert data:
   

   IntPtr pTextResultArray = IntPtr.Zero;
   
   DBR_GetAllTextResults(hBarcode, ref pTextResultArray);
   
   if (pTextResultArray != IntPtr.Zero)
   {
       string[]? resultArray = null;
       TextResultArray? results = (TextResultArray?)Marshal.PtrToStructure(pTextResultArray, typeof(TextResultArray));
       if (results != null)
       {
           int count = results.Value.resultsCount;
           if (count > 0)
           {
               IntPtr[] barcodes = new IntPtr[count];
               Marshal.Copy(results.Value.results, barcodes, 0, count);
               resultArray = new string[count];
   
               for (int i = 0; i < count; i++)
               {
                   PTextResult? result = (PTextResult?)Marshal.PtrToStructure(barcodes[i], typeof(PTextResult));
                   if (result != null)
                   {
                       resultArray[i] = result.Value.barcodeText;
                   }
               }
           }
       }
   
       DBR_FreeTextResults(ref pTextResultArray);
   
       return resultArray;
   }
   

5. Once the communication problem between managed and unmanaged code is solved, we can define some high-level C# methods:
   

   public class BarcodeQRCodeReader
   {
       private IntPtr hBarcode;
       private static string? licenseKey;
   
       public static void InitLicense(string license) {
           byte[] errorMsg = new byte[512];
           licenseKey = license;
           DBR_InitLicense(license, errorMsg, 512);
           Console.WriteLine(Encoding.ASCII.GetString(errorMsg) + "\n");
       }
   
       private BarcodeQRCodeReader()
       {
           hBarcode = DBR_CreateInstance();
       }
   
       public static BarcodeQRCodeReader Create()
       {
           if (licenseKey == null)
           {
               throw new Exception("Please call InitLicense first.");
           }
           return new BarcodeQRCodeReader();
       }
   
       ~BarcodeQRCodeReader()
       {
           if (hBarcode != IntPtr.Zero)
           {
               DBR_DestroyInstance(hBarcode);
               hBarcode = IntPtr.Zero;
           }
       }
   
       public void Destroy()
       {
           if (hBarcode != IntPtr.Zero)
           {
               DBR_DestroyInstance(hBarcode);
               hBarcode = IntPtr.Zero;
           }
       }
   
       public string[]? DecodeFile(string filename)
       {
           if (hBarcode == IntPtr.Zero) return null;
   
           int ret = DBR_DecodeFile(hBarcode, filename, "");
           return OutputResults();
       }
   }
   

6. Build the source code to generate the *.dll file.
   

   dotnet build --configuration Release
   

How to Generate and Publish NuGet Package

To generate the *.nupkg file, the easiest way is to add <GeneratePackageOnBuild>true</GeneratePackageOnBuild> to the *.csproj file:

<PropertyGroup>
  ...
  <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
  ...
</PropertyGroup>

Then the *.nupkg file will be generated automatically when you build the project.

Our package contains some native library files. To pack them into the *.nupkg file correctly, we set the corresponding PackagePath in *.csproj file according to the Runtime Identifier:

<ItemGroup>
  <None CopyToOutputDirectory="Always" Include="DynamsoftBarcodeReader.dll" Pack="true" PackagePath="runtimes/win-x64/native/DynamsoftBarcodeReader.dll" />
  <None CopyToOutputDirectory="Always" Include="vcomp110.dll" Pack="true" PackagePath="runtimes/win-x64/native/vcomp110.dll" />
  <None CopyToOutputDirectory="Always" Include="libDynamsoftBarcodeReader.dylib" Pack="true" PackagePath="runtimes/osx-x64/native/libDynamsoftBarcodeReader.dylib" />
  <None CopyToOutputDirectory="Always" Include="libDynamsoftBarcodeReader.so" Pack="true" PackagePath="runtimes/linux-x64/native/libDynamsoftBarcodeReader.so" />
</ItemGroup>

As the *.nupkg file is ready, we can publish it to the NuGet Gallery either via the dotnet command:

dotnet nuget push *.nupkg -k <api-key> -s https://api.nuget.org/v3/index.json

or the NuGet online page.

Here is the final page of BarcodeQRCodeSDK:
https://www.nuget.org/packages/BarcodeQRCodeSDK/

How to Add a .NET Library Project as a Reference Locally

For source code, add <ProjectReference> in *.csproj file:

<ItemGroup>
    <ProjectReference Include="..\..\BarcodeQRCodeSDK.csproj" />
</ItemGroup>

For generated *.nupkg file, add the package directory to NuGet source list and then install the package via dotnet add package:

dotnet nuget add source <package directory>
dotnet add package <package name>

A Simple .NET 6 Command-line Example

1. Create a new .NET console app:
   

   dotnet new console -o Test
   

2. Install the .NET Barcode and QR Code SDK:
   

   dotnet add package BarcodeQRCodeSDK
   

3. Use the following code to decode barcode and QR code from an image file:
   

   using System;
   using System.Runtime.InteropServices;
   using Dynamsoft;
   
   namespace Test
   {
       class Program
       {
           static void Main(string[] args)
           {
               BarcodeQRCodeReader.InitLicense("LICENSE-KEY");
               BarcodeQRCodeReader? reader = null;
               try {
                   reader = BarcodeQRCodeReader.Create();
                   Console.WriteLine("Please enter an image file: ");
                   string? filename = Console.ReadLine();
                   if (filename != null) {
                       string[]? results = reader.DecodeFile(filename);
                       if (results != null) {
                           foreach (string result in results) {
                               Console.WriteLine(result);
                           }
                       }
                       else {
                           Console.WriteLine("No barcode found.");
                       }
                   }
               }
               catch (Exception e)
               {
                   Console.WriteLine(e.Message);
               }
               finally
               {
                   if (reader != null)
                   {
                       reader.Destroy();
                   }
               }
           }
       }
   }
   

4. Run the application in Windows, Linux or macOS:
   

   dotnet run
   

   

Source Code

https://github.com/yushulx/dotnet-barcode-qr-code-sdk