There was a need to create .proto definition files from the definitions of a reverse engineered database first project. The approach taken was that of using System.Emit to generate the type definitions and feed those to protobuf-net and use its ability to generate the .proto files.
There are only three classes needed:
- ContextFinder
- ClassGenerator
- Program
The ContextFinder is pretty straight forward. It uses reflection to get all the generic parameters of DbSet<> properties within a DbContext. Then, ClassGenerator is used to copy the properties of the Types we harvested into a new type with the addition of adding ProtoContract and ProtoMember appropriately. Then, the Program class just loads the assembly from the file specified and runs the previously two mentioned classes.
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| public class ClassGenerator | |
| { | |
| private readonly ModuleBuilder _moduleBuilder; | |
| public ClassGenerator() | |
| { | |
| var an = new AssemblyName("DynamicProtoAssembly"); | |
| AssemblyBuilder assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(an,AssemblyBuilderAccess.Run); | |
| _moduleBuilder = assemblyBuilder.DefineDynamicModule("DynamicProtoModule"); | |
| } | |
| public Type CreateType(Type typeToCopy) | |
| { | |
| TypeBuilder tb = _moduleBuilder.DefineType(typeToCopy.Name + "Proto", | |
| TypeAttributes.Public | | |
| TypeAttributes.Class | | |
| TypeAttributes.AutoClass | | |
| TypeAttributes.AnsiClass | | |
| TypeAttributes.BeforeFieldInit | | |
| TypeAttributes.AutoLayout, | |
| null); | |
| ConstructorBuilder constructor = tb.DefineDefaultConstructor(MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.RTSpecialName); | |
| var ci = typeof(ProtoContractAttribute).GetConstructor(new Type[0]); | |
| var builder = new CustomAttributeBuilder(ci,new object[0]); | |
| tb.SetCustomAttribute(builder); | |
| var propertiesToCopy = typeToCopy.GetProperties(); | |
| for (int i = 0; i < propertiesToCopy.Length; i++) | |
| { | |
| var propertyInfo = propertiesToCopy[i]; | |
| CreateProperty(tb,propertyInfo.Name,propertyInfo.PropertyType,i); | |
| } | |
| return tb.CreateType(); | |
| } | |
| private static void CreateProperty(TypeBuilder tb, string propertyName, Type propertyType, int i) | |
| { | |
| FieldBuilder fieldBuilder = tb.DefineField("_" + propertyName, propertyType, FieldAttributes.Private); | |
| PropertyBuilder propertyBuilder = tb.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, null); | |
| MethodBuilder getPropMthdBldr = tb.DefineMethod("get_" + propertyName, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, propertyType, Type.EmptyTypes); | |
| ILGenerator getIl = getPropMthdBldr.GetILGenerator(); | |
| getIl.Emit(OpCodes.Ldarg_0); | |
| getIl.Emit(OpCodes.Ldfld, fieldBuilder); | |
| getIl.Emit(OpCodes.Ret); | |
| MethodBuilder setPropMthdBldr = | |
| tb.DefineMethod("set_" + propertyName, | |
| MethodAttributes.Public | | |
| MethodAttributes.SpecialName | | |
| MethodAttributes.HideBySig, | |
| null, new[] { propertyType }); | |
| ILGenerator setIl = setPropMthdBldr.GetILGenerator(); | |
| Label modifyProperty = setIl.DefineLabel(); | |
| Label exitSet = setIl.DefineLabel(); | |
| setIl.MarkLabel(modifyProperty); | |
| setIl.Emit(OpCodes.Ldarg_0); | |
| setIl.Emit(OpCodes.Ldarg_1); | |
| setIl.Emit(OpCodes.Stfld, fieldBuilder); | |
| setIl.Emit(OpCodes.Nop); | |
| setIl.MarkLabel(exitSet); | |
| setIl.Emit(OpCodes.Ret); | |
| propertyBuilder.SetGetMethod(getPropMthdBldr); | |
| propertyBuilder.SetSetMethod(setPropMthdBldr); | |
| var ci = typeof(ProtoMemberAttribute).GetConstructor(new [] { typeof(int) }); | |
| var builder = new CustomAttributeBuilder(ci, new object[] { i + 1 }); | |
| propertyBuilder.SetCustomAttribute(builder); | |
| } | |
| } |
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| public class ContextFinder | |
| { | |
| public IEnumerable<Type> GetAllTypesInContextDbSets(Assembly assembly) | |
| { | |
| return GetContextTypes(assembly) | |
| .Select(x => GetDataSetTypes(x)) | |
| .SelectMany(x => x) | |
| .Select(x => x.GetGenericArguments()[0]); | |
| } | |
| private IEnumerable<Type> GetContextTypes(Assembly assembly) | |
| { | |
| return assembly.GetTypes() | |
| .Where(myType => myType.IsClass && !myType.IsAbstract && myType.IsSubclassOf(typeof(DbContext))); | |
| } | |
| private IEnumerable<Type> GetDataSetTypes(Type context) | |
| { | |
| return context.GetProperties() | |
| .Select(x => x.PropertyType) | |
| .Where(x => x.IsGenericType && x.GetGenericTypeDefinition() == typeof(DbSet<>)); | |
| } | |
| } |
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| class Program | |
| { | |
| static void Main(string[] args) | |
| { | |
| if (args.Length < 1) | |
| { | |
| Console.WriteLine("The first argument should be a path to the assembly"); | |
| return; | |
| } | |
| Assembly assembly = Assembly.LoadFile(args[0]); | |
| ContextFinder finder = new ContextFinder(); | |
| var types = finder.GetAllTypesInContextDbSets(assembly); | |
| ClassGenerator generator = new ClassGenerator(); | |
| var protoTypes = types.Select(x => generator.CreateType(x)); | |
| foreach (var protoType in protoTypes) | |
| { | |
| Console.WriteLine(GenerateProtoFile(protoType)); | |
| } | |
| } | |
| private static string GenerateProtoFile(Type protoType) | |
| { | |
| MethodInfo methodInfo = typeof(Serializer).GetMethod(nameof(Serializer.GetProto),new [] {typeof(ProtoSyntax)}); | |
| MethodInfo genericMethod = methodInfo.MakeGenericMethod(protoType); | |
| return (string) genericMethod.Invoke(null, new object[] { ProtoSyntax.Proto3 }); | |
| } | |
| } |
