渐近分析“o”到“O”的转换(Asymptotic analysis “o” to “O” conversion)

 您可以使用AddModelError方法将自定义错误消息添加到Model状态字典中。 validationSummary / ValidationMessageFor辅助方法在被调用时从模型状态字典中读取验证错误。 
 
 第一个参数是错误消息的关键。 如果您传递string.empty作为值，则您传递的自定义错误消息将由ValidationSummary辅助方法呈现 
 
ModelState.AddModelError(string.Empty,"Incorrect user name or password.");
return View(p);
 
 如果要通过输入元素（一个ValidationMessageFor呈现）呈现错误消息，则可以在调用AdddModelError方法时传递属性名称作为键值。 
 
ModelState.AddModelError(nameof(User.Password),"Incorrect password");
return View();

You can add the custom error message to the Model state dictionary using the AddModelError method. The validationSummary /ValidationMessageFor helper methods reads the validation errors from model state dictionary when it gets called.
 
The first parameter is the key for the error message. If you pass string.empty as the value the custom error message you are passing will be rendered by the ValidationSummary helper method
 
ModelState.AddModelError(string.Empty,"Incorrect user name or password.");
return View(p);
 
If you want to render the error message by the input element (The one ValidationMessageFor renders), you may pass the property name as the key value when calling the AdddModelError method.
 
ModelState.AddModelError(nameof(User.Password),"Incorrect password");
return View();