Comment c = this.Bind();
ModelValidationResult result = this.Validate(c);
if (!result.IsValid) {
	StringBuilder respStr = new StringBuilder();
	foreach (ModelValidationError err in result.Errors) {
		foreach (string memberName in err.MemberNames) {
			respStr.Append(err.GetMessage(memberName) + ", ");
		}
	}
	return Response.AsJson(new { error_message = "Invalid data. " + respStr.ToString() }, HttpStatusCode.BadRequest);
}