add: options for DllImport and LibraryImport

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -2003,7 +2003,7 @@ internal static bool {Helpers.TryGetNativeToManagedMappingIdentifier}(IntPtr nat
 
             if (hasReturn && isPrimitive && !isSetter)
             {
-                WriteLine($"return { Helpers.ReturnIdentifier};");
+                WriteLine($"return {Helpers.ReturnIdentifier};");
                 return;
             }
 
@@ -2322,8 +2322,7 @@ internal static bool {Helpers.TryGetNativeToManagedMappingIdentifier}(IntPtr nat
                 @class.HasNonTrivialDestructor && !@class.IsAbstract)
             {
                 NativeLibrary library;
-                if (!Options.CheckSymbols ||
-                    Context.Symbols.FindLibraryBySymbol(dtor.Mangled, out library))
+                if (!Options.CheckSymbols || Context.Symbols.FindLibraryBySymbol(dtor.Mangled, out library))
                 {
                     // Normally, calling the native dtor should be controlled by whether or not we
                     // we own the underlying instance. (i.e. Helpers.OwnsNativeInstanceIdentifier).
@@ -3559,12 +3558,24 @@ internal static{(@new ? " new" : string.Empty)} {printedClass} __GetInstance({Ty
                 return;
 
             PushBlock(BlockKind.InternalsClassMethod);
-            var callConv = function.CallingConvention.ToInteropCallConv();
 
-            WriteLine("[SuppressUnmanagedCodeSecurity, DllImport(\"{0}\", EntryPoint = \"{1}\", CallingConvention = __CallingConvention.{2})]",
+            string callConv = "";
+            string libImportType = "LibraryImport";
+            string functionKeyword = "partial";
+
+            if (Options.LibraryImportType == LibraryImportType.DllImport)
+            {
+                callConv = $", CallingConvention = CallingConvention.{function.CallingConvention.ToInteropCallConv()}";
+                libImportType = "DllImport";
+                functionKeyword = "extern";
+            }
+
+            WriteLine("[SuppressUnmanagedCodeSecurity, {0}(\"{1}\", EntryPoint = \"{2}\"{3})]",
+            libImportType,
             GetLibraryOf(function),
             function.Mangled,
-                callConv);
+            callConv
+            );
 
             if (function.ReturnType.Type.IsPrimitiveType(PrimitiveType.Bool))
                 WriteLine("[return: MarshalAs(UnmanagedType.I1)]");
@@ -3572,7 +3583,9 @@ internal static{(@new ? " new" : string.Empty)} {printedClass} __GetInstance({Ty
             TypePrinterResult retType;
             var @params = GatherInternalParams(function, out retType);
 
-            WriteLine("internal static extern {0} {1}({2});", retType,
+            WriteLine("internal static {0} {1} {2}({3});",
+                      functionKeyword,
+                      retType,
                       GetFunctionNativeIdentifier(function),
                       string.Join(", ", @params));
             PopBlock(NewLineKind.BeforeNextBlock);

src/Generator/Options.cs

@@ -2,11 +2,13 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Reflection;
+using System.Runtime.Versioning;
 using System.Text;
 using CppSharp.AST;
 using CppSharp.Generators;
 using CppSharp.Passes;
-
+using Module = CppSharp.AST.Module;
 namespace CppSharp
 {
     public enum GenerationOutputMode
@@ -15,10 +17,28 @@ namespace CppSharp
         FilePerUnit
     }
 
+
+    /// <summary>
+    /// Specifies the type of interop attribute to be used in the generated bindings.
+    /// </summary>
+    public enum LibraryImportType
+    {
+        /// <summary>
+        /// Represents the <see cref="System.Runtime.InteropServices.DllImportAttribute"/> attribute,
+        /// </summary>
+        DllImport,
+
+        /// <summary>
+        /// Represents the <see cref="System.Runtime.InteropServices.LibraryImportAttribute"/> attribute,
+        /// </summary>
+        LibraryImport
+    }
+
     public class DriverOptions
     {
         public DriverOptions()
         {
+
             OutputDir = Directory.GetCurrentDirectory();
 
             SystemModule = new Module("Std") { OutputNamespace = string.Empty };
@@ -84,6 +104,14 @@ namespace CppSharp
 
         public string OutputDir;
 
+        /// <summary>
+        /// C# only: Specifies the type of interop attribute to be used in the generated bindings.
+        /// Default value is dependent on target framework version
+        /// </summary>
+
+        public LibraryImportType LibraryImportType { get; set; } = GetLibraryImportType();
+
+
         public bool OutputInteropIncludes;
         public bool GenerateFunctionTemplates;
         /// <summary>
@@ -111,7 +139,7 @@ namespace CppSharp
         /// </summary>
         public bool GenerateObjectOverrides;
 
-        //List of include directories that are used but not generated
+        // List of include directories that are used but not generated
         public List<string> NoGenIncludeDirs;
 
         /// <summary>
@@ -261,6 +289,22 @@ namespace CppSharp
 
         public TranslationUnitPassCallBack TranslationUnitPassPostCallBack { get; set; }
 
+       internal static LibraryImportType GetLibraryImportType()
+        {
+
+            var targetFrameworkInfo = Assembly.GetCallingAssembly()
+            .GetCustomAttribute<TargetFrameworkAttribute>()
+            .FrameworkName.Split(",");
+
+            var targetFrameworkVer =  float.Parse(targetFrameworkInfo[1].Split("Version=")[1].Trim('v'));
+             if (targetFrameworkVer >= 7.0) 
+             {
+                return LibraryImportType.LibraryImport;
+             } 
+             
+             return LibraryImportType.DllImport;
+        }
+
         #endregion
     }
 
@@ -269,6 +313,7 @@ namespace CppSharp
         public InvalidOptionException(string message) :
             base(message)
         {
+        
         }
     }
 }