Catel.Fody.Weaving.Argument.ArgumentWeaver.GetParameterOrFieldForExpressionArgumentCheck C# (CSharp) Method

        private object GetParameterOrFieldForExpressionArgumentCheck(MethodDefinition method, Collection<Instruction> instructions, Instruction instruction)
        {
            TypeReference displayClassType = null;
            FieldDefinition parameterFieldDefinition = null;

            // This logic is used for finding the parameter:

            // 1) Find the display class
            // 2) Find the field used
            // 3) Check with which parameter the field is assigned

            var index = instructions.IndexOf(instruction);
            for (var i = index; i >= 0; i--)
            {
                var innerInstruction = instructions[i];

                if (innerInstruction.IsOpCode(OpCodes.Ldtoken))
                {
                    if (displayClassType == null)
                    {
                        // First call to ldtoken with FieldDefinition contains the display class type
                        parameterFieldDefinition = GetFieldDefinition(innerInstruction);
                        if (parameterFieldDefinition != null)
                        {
                            displayClassType = parameterFieldDefinition.DeclaringType;
                        }
                    }
                }

                if (innerInstruction.IsOpCode(OpCodes.Stfld))
                {
                    var fieldDefinition = innerInstruction.Operand as FieldDefinition;
                    if (fieldDefinition == null)
                    {
                        var fieldReference = innerInstruction.Operand as FieldReference;
                        if (fieldReference != null)
                        {
                            fieldDefinition = fieldReference.Resolve();
                        }
                    }

                    if (fieldDefinition == parameterFieldDefinition)
                    {
                        // We found it, now check 1 instruction back for the actual parameter
                        var finalInstruction = instructions[i - 1];

                        var finalFieldDefinition = finalInstruction.Operand as FieldDefinition;
                        if (finalFieldDefinition != null)
                        {
                            return finalFieldDefinition;
                        }

                        var parameterDefinition = finalInstruction.Operand as ParameterDefinition;
                        if (parameterDefinition != null)
                        {
                            return parameterDefinition;
                        }
                    }
                }
            }

            return null;
        }