一个asp.net core项目，一定包含了各种的实体，在RESTful api里面，有很多的参数传递，不建立实体则大量的参数需要自定验证正确性，并且Action上面会写的密密麻麻的参数
在asp.net 2.0的时候，就推出了ModelState，顾名思义，这个是模型状态，用于验证实体对象的
如何模型验证
用法是在需要验证的地方打上继承了ValidationAttribute的特性，比如常见的RequiredAttribute，这个是验证对象是否存在
???/// <summary> ???/// Admin Request Model ???/// </summary> ???public class AdminRequestModel ???{ ???????/// <summary> ???????/// User ???????/// </summary> ???????[Required] ???????public string User { get; set; } ???????/// <summary> ???????/// Account ???????/// </summary> ???????[Required] ???????public string Account { get; set; } ???}这是一个实体
我们要验证的Model里是“User”属性和“Account”属性不能为空
写在Action上面
???????/// <summary> ???????/// Test Admin ???????/// </summary> ???????/// <param name="model"></param> ???????/// <returns></returns> ???????[HttpPost("Admin")] ???????public ResponseModel Admin(AdminRequestModel model) ???????{ ???????????return new AdminResponseModel() ???????????{ ???????????????User = model.User ???????????}; ???????}在asp.net core 2.1之前版本的web api则改为
???????/// <summary> ???????/// Test Admin ???????/// </summary> ???????/// <param name="model"></param> ???????/// <returns></returns> ???????[HttpPost("Admin")] ???????public ResponseModel Admin([FromForm] AdminRequestModel model) ???????{ ???????????return new AdminResponseModel() ???????????{ ???????????????User = model.User ???????????}; ???????}进入了Action的就是通过了基础模型验证的实体对象，数据库操作之类的业务验证，就在Action里面处理
怎么启用模型验证
全局过滤器
???/// <summary> ???/// Gold Filter Validate Model ???/// </summary> ???public class GoldModelFilter : IActionFilter ???{ ???????/// <summary> ???????/// Action Before ???????/// </summary> ???????/// <param name="context"></param> ???????public void OnActionExecuted(ActionExecutedContext context) ???????{ ???????} ???????/// <summary> ???????/// Action After ???????/// </summary> ???????/// <param name="context"></param> ???????public void OnActionExecuting(ActionExecutingContext context) ???????{ ???????????if (!context.ModelState.IsValid) ???????????????throw new ValidateException( ???????????????????context.ModelState.Values ???????????????????????.FirstOrDefault(item => item.Errors.Count > 0 ???????????????????????) ???????????????????????.Errors.FirstOrDefault().ErrorMessage ???????????????); ???????} ???}然后在
Startup.cs的ConfigureService内写的AddMvc改为
???????????services.AddMvc(options=> { ???????????????options.Filters.Add<GoldModelFilter>(); ???????????}));我们不需要全局验证的则这样写
???public class ModelFilterAttribute:ActionFilterAttribute ???{ ???????/// <summary> ???????/// Action Before ???????/// </summary> ???????/// <param name="context"></param> ???????public override void OnActionExecuted(ActionExecutedContext context) ???????{ ???????????//leave out ???????} ???????/// <summary> ???????/// Action After ???????/// </summary> ???????/// <param name="context"></param> ???????public override void OnActionExecuting(ActionExecutingContext context) ???????{ ???????????//leave out ???????} ???}是不是很像，是的，就是一样的，只是一个是特性，一个是过滤器，内部的流程也差不多
ActionFilterAttribute还有很多东西，就暂不赘述了
我们在需要模型验证的Action上面打上特性就可以了
如何扩展自定义模型验证
CustomValidationAttribute，顾名思义这个是做自定义模型验证的，支持给属性、字段、方法、参数和实体对象验证的
他有两个参数，参数1是自定义的验证类Type，参数2是方法名
自定义验证类需要是公开类，自定义方法也是公开方法
方法参数1是object类型，参数2是ValidationContext类型
参数1是验证的内容，参数2是验证的上下文
包括
DisplayName 描述名
MemberName 成员名
ObjectInstance 整个验证的实体
ObjectType 整个验证的实体类型
还一个方法GetService
这个是获取服务的，依赖注入里面的服务，可以通过这个取出来
如果我们要对之前的AdminRequestModel这个实体验证User是否等于Account，不等于，则写一条错误日志，然后验证失败
???/// <summary> ???/// Admin Validate ???/// </summary> ???public class AdminValidate ???{ ???????/// <summary> ???????/// Ordinary Validate ???????/// </summary> ???????/// <param name="value"></param> ???????/// <param name="validationContext"></param> ???????/// <returns></returns> ???????public static ValidationResult Ordinary(object value, ValidationContext validationContext) ???????{ ???????????if (value is AdminRequestModel model) ???????????{ ???????????????if (!model.User.Equals(model.Account)) ???????????????{ ???????????????????var logger = validationContext.GetService(typeof(ILogger<AdminValidate>)) as ILogger<AdminValidate>; ???????????????????logger.LogError("User not equals Account"); ???????????????????return new ValidationResult("User not equals Account"); ???????????????} ???????????????return ValidationResult.Success; ???????????} ???????????return new ValidationResult("Type Error"); ???????} ???}AdminRequestModel上面加一行[CustomValidation(typeof(AdminValidate), "Ordinary")]
这种是低复用的场景下，给特定的做验证的，如果我们这种验证很多，而且很多处都有相似的验证，那么可以写一个特性，继承ValidationAttribute
这个的验证的有两种场景，单纯的内容验证，没有功能性的，比如上面这种，验证失败，悄悄写一条错误日志，甚至发一个预警邮件
那么重构两个方法FormatErrorMessage和IsValid，前者返回错误信息，后者是验证的
除了验证，还有一些功能性的
那么请重构IsValid方法
代码和AdminValidate.Ordinary雷同
扩展
如果我们的过滤特性里面也有一些功能性呢？
???/// <summary> ???/// Register Service Action Filter ???/// </summary> ???public class ServiceActionFilterAttribute : ActionFilterAttribute ???{ ???????private ILogger<ServiceActionFilterAttribute> Logger { get; } ???????/// <summary> ???????/// Generate ???????/// </summary> ???????/// <param name="logger"></param> ???????public ServiceActionFilterAttribute(ILogger<ServiceActionFilterAttribute> logger) ???????{ ???????????Logger = logger; ???????} ???????/// <summary> ???????/// Action Before ???????/// </summary> ???????/// <param name="context"></param> ???????public override void OnActionExecuted(ActionExecutedContext context) ???????{ ???????????//leave out ???????} ???????/// <summary> ???????/// Action After ???????/// </summary> ???????/// <param name="context"></param> ???????public override void OnActionExecuting(ActionExecutingContext context) ???????{ ???????????//leave out ???????} ???}这样是不能打在Action上面了
这个时候，我们就要掏出ServiceFilterArribute或者TypeFilterAttribute
???????/// <summary> ???????/// Test Admin ???????/// </summary> ???????/// <param name="model"></param> ???????/// <returns></returns> ???????[HttpPost("AdminDIFilterAttibute")] ???????[ServiceFilter(typeof(ServiceActionFilterAttribute))] ???????public ResponseModel AdminDIFilterAttibute(AdminRequestModel model) ???????{ ???????????return new AdminResponseModel() ???????????{ ???????????????User = model.User ???????????}; ???????}前者是Type必须注册在依赖注入容器里面的，后者是不需要的
项目地址:
https://github.com/htrlq/AspNetCoreTemplate
从零写一个Asp.net core手脚架（模型验证）
原文地址：https://www.cnblogs.com/NCoreCoder/p/10385459.html