How to handle multiple module filed using dnlib C#

<pre>dnlib.DotNet.Writer.ModuleWriterException: Field 'System.String Api.Class1::MyField1' (0x04000000) is not defined in this module 'Test.exe'. A field was removed that is still referenced by this module. Error occurred after metadata event BeginWriteMethodBodies during writing method 'System.Void TEST._fTest::Patched()' (0x060000A8).
   at dnlib.DotNet.DummyLogger.Log(Object sender, LoggerEvent loggerEvent, String format, Object[] args)
   at dnlib.DotNet.Writer.ModuleWriterBase.dnlib.DotNet.ILogger.Log(Object sender, LoggerEvent loggerEvent, String format, Object[] args)
   at dnlib.DotNet.Writer.Metadata.Error(String message, Object[] args)
   at dnlib.DotNet.Writer.NormalMetadata.GetRid(FieldDef fd)
   at dnlib.DotNet.Writer.Metadata.AddMDTokenProvider(IMDTokenProvider tp)
   at dnlib.DotNet.Writer.Metadata.GetToken(Object o)
   at dnlib.DotNet.Writer.MethodBodyWriter.WriteInlineField(ArrayWriter& writer, Instruction instr)
   at dnlib.DotNet.Writer.MethodBodyWriterBase.WriteOperand(ArrayWriter& writer, Instruction instr)
   at dnlib.DotNet.Writer.MethodBodyWriterBase.WriteInstruction(ArrayWriter& writer, Instruction instr)
   at dnlib.DotNet.Writer.MethodBodyWriterBase.WriteInstructions(ArrayWriter& writer)
   at dnlib.DotNet.Writer.MethodBodyWriter.WriteTinyHeader()
   at dnlib.DotNet.Writer.MethodBodyWriter.Write()
   at dnlib.DotNet.Writer.Metadata.WriteMethodBodies()
   at dnlib.DotNet.Writer.Metadata.Create()
   at dnlib.DotNet.Writer.Metadata.CreateTables()
   at dnlib.DotNet.Writer.ModuleWriter.WriteImpl()
   at dnlib.DotNet.Writer.ModuleWriterBase.Write(Stream dest)
   at dnlib.DotNet.Writer.ModuleWriterBase.Write(String fileName)
   at dnlib.DotNet.ModuleDef.Write(String filename)  

<pre lang="C#"><pre>static void Main(string[] args)
 {
     Console.WriteLine(args[0]);
     string _sRoot = args[0];
     string _sRootApi = args[0].Replace("Test.exe", "Api.dll");
     //AssemblyDef assembly = AssemblyDef.Load(_sRoot);
     ModuleContext modCtx = ModuleDefMD.CreateModuleContext();
     ModuleDefMD module = ModuleDefMD.Load(_sRoot, modCtx);


     ModuleContext Api_modCtx = ModuleDefMD.CreateModuleContext();
     ModuleDefMD Api_module = ModuleDefMD.Load(_sRootApi, Api_modCtx);
     try
     {
         Load_DLL_ClassName(Api_module);
         Patched(module, Api_module);
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.ToString());
     }

     try
     {
         Api_module.Write(_sRootApi.Replace(".dll", "of.dll"));
         module.Write(args[0].Replace(".exe", "of.exe"));

     }
     catch (Exception ex)
     {
         File.WriteAllText(Application.StartupPath.ToString() + "\\Error.txt", ex.ToString());
         MessageBox.Show(ex.ToString());
     }
 }
 static TypeDef Class1;
 public static void Load_DLL_ClassName(ModuleDef module)
 {
     foreach (TypeDef type in module.Types)
     {
         if (type.Name.ToString() == "Class1")
         {
             Class1 = type;
             break;
         }
     }
 }
 static int _inum = 0;
 public static FieldDefUser CreateFiled(ModuleDef module, string Data)
 {
     // Create a public static System.Int32 field called MyField
     var field1 = new FieldDefUser("MyField" + _inum.ToString(),
                     new FieldSig(module.CorLibTypes.String),
                     FieldAttributes.Public | FieldAttributes.Static);
     Class1.Fields.Add(field1);
     return field1;
 }
 public static void Patched(ModuleDef module, ModuleDef Api_module)
 {
     foreach (TypeDef type in module.Types)
     {
         foreach (MethodDef method in type.Methods)
         {
             if (method.Name != "Patched")
             {
                 continue;
             }
             if (method.Body == null) continue;


             method.Body.SimplifyBranches();
             for (int i = 0; i < method.Body.Instructions.Count; i++)
             {
                 if (method.Body.Instructions[i].OpCode == OpCodes.Ldstr)
                 {
                     string _sValue = method.Body.Instructions[i].Operand.ToString();
                     FieldDefUser ff = CreateFiled(module, _sValue);
                     _inum++;
                     method.Body.Instructions[i].OpCode = OpCodes.Nop;
                     method.Body.Instructions.Insert(i + 1, OpCodes.Ldsfld.ToInstruction(ff));
                     i += 1;
                 }
             }
         }
     }
 }