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本地化ASP.NET core模型绑定错误消息

默认错误消息：

MissingBindRequiredValueAccessor    A value for the '{0}' property was not provided.
MissingKeyOrValueAccessor           A value is required.
ValueMustNotBeNullAccessor          The value '{0}' is invalid. 
AttemptedValueIsInvalidAccessor     The value '{0}' is not valid for {1}.
UnknownValueIsInvalidAccessor       The supplied value is invalid for {0}.
ValueIsInvalidAccessor              The value '{0}' is invalid.
ValueMustBeANumberAccessor          The field {0} must be a number.

MissingRequestBodyRequiredValueAccessor       A non-empty request body is required.
NonPropertyAttemptedValueIsInvalidAccessor    The value '{0}' is not valid.
NonPropertyUnknownValueIsInvalidAccessor      The supplied value is invalid.
NonPropertyValueMustBeANumberAccessor         The field must be a number.

若要本地化ASP.NET Core 模型绑定错误消息，请按照下列步骤操作：

创建资源文件 - 在解决方案的Resources文件夹下创建资源文件，并将文件命名为ModelBindingMessages.resx。名称可以是其他任何名称，但我们将使用它来创建本地化程序。
添加资源键 - 打开资源文件并添加要用于本地化错误消息的键和值。我使用了键和值
配置选项 - 在ConfigureServices方法中，添加时Mvc，配置其选项以设置以下内容的消息访问者ModelBindingMessageProvider

 1    services.AddMvc(options =>
 2             {
 3                 IStringLocalizerFactory F = services.BuildServiceProvider().
 4                 GetService<IStringLocalizerFactory>();
 5                 IStringLocalizer L = F.Create("ModelBindingMessages",
 6                     "AspNetCoreLocalizationSample");
 7                 options.ModelBindingMessageProvider.
 8                 SetValueIsInvalidAccessor((x) => L["The value '{0}' is invalid."]);
 9                 options.ModelBindingMessageProvider.SetValueMustBeANumberAccessor(
10                     (x) =>L["The field {0} must be a number."]);
11                 options.ModelBindingMessageProvider.SetMissingBindRequiredValueAccessor(
12                     (x) => L["A value for the '{0}' property was not provided.", x]);
13                 options.ModelBindingMessageProvider.SetAttemptedValueIsInvalidAccessor(
14                     (x, y) => L["The value '{0}' is not valid for {1}.", x, y]);
15                 options.ModelBindingMessageProvider.SetMissingKeyOrValueAccessor(
16                     () => L["A value is required."]);
17                 options.ModelBindingMessageProvider.SetUnknownValueIsInvalidAccessor(
18                     (x) => L["The supplied value is invalid for {0}.", x]);
19                 options.ModelBindingMessageProvider.SetValueMustNotBeNullAccessor(
20                     (x) => L["Null value is invalid.", x]);
21             }).AddDataAnnotationsLocalization()
22     .AddViewLocalization();
23     services.Configure<RequestLocalizationOptions>(options =>
24     {
25         var supportedCultures = new[]{new CultureInfo("en"), new CultureInfo("zh-cn")};
26         options.DefaultRequestCulture = new RequestCulture("en", "en");
27         options.SupportedCultures = supportedCultures;
28         options.SupportedUICultures = supportedCultures;
29     });

还要在Configure方法开头添加此代码：

1 var supportedCultures = new[] { new CultureInfo("en"), new CultureInfo("zh-CN") };
2 app.UseRequestLocalization(new RequestLocalizationOptions()
3 {
4     DefaultRequestCulture = new RequestCulture(new CultureInfo("en")),
5     SupportedCultures = supportedCultures,
6     SupportedUICultures = supportedCultures
7 });

关于属性DisplayAttribute

通过查看源码在 Microsoft.AspNetCore.Mvc.DataAnnotations.Internal.DataAnnotationsMetadataProvider中有IDisplayMetadataProvider的实现
主要是判断DisplayName不为空和ResourceType为空的时候使用IStringLocalizerFactory
代码片段如下：

  1    var dataTypeAttribute = attributes.OfType<DataTypeAttribute>(). 
  2 if (displayFormatAttribute == null && dataTypeAttribute != null)
  3             {
  4                 displayFormatAttribute = dataTypeAttribute.DisplayFormat;
  5             }
  6             var displayMetadata = context.DisplayMetadata;
  7 
  8             // ConvertEmptyStringToNull
  9             if (displayFormatAttribute != null)
 10             {
 11                 displayMetadata.ConvertEmptyStringToNull = displayFormatAttribute.
 12                     ConvertEmptyStringToNull;
 13             }
 14             // DataTypeName
 15             if (dataTypeAttribute == null)
 16             {
 17                 if (displayFormatAttribute != null && !displayFormatAttribute.HtmlEncode)
 18                 {
 19                     displayMetadata.DataTypeName = DataType.Html.ToString();
 20                 }
 21             }
 22             else
 23             {
 24                 displayMetadata.DataTypeName = dataTypeAttribute.GetDataTypeName();
 25             }
 26 
 27             var containerType = context.Key.ContainerType ?? context.Key.ModelType;
 28             IStringLocalizer localizer = null;
 29             if (_stringLocalizerFactory != null && _localizationOptions.DataAnnotationLocalizerProvider != null)
 30             {
 31                 localizer = _localizationOptions.DataAnnotationLocalizerProvider(containerType, _stringLocalizerFactory);
 32             }
 33 
 34             // Description
 35             if (displayAttribute != null)
 36             {
 37                 if (localizer != null &&
 38                     !string.IsNullOrEmpty(displayAttribute.Description) &&
 39                     displayAttribute.ResourceType == null)
 40                 {
 41                     displayMetadata.Description = () => localizer[displayAttribute.Description];
 42                 }
 43                 else
 44                 {
 45                     displayMetadata.Description = () => displayAttribute.GetDescription();
 46                 }
 47             }
 48 
 49             // DisplayFormatString
 50             if (displayFormatAttribute != null)
 51             {
 52                 displayMetadata.DisplayFormatString = displayFormatAttribute.DataFormatString;
 53             }
 54 
 55             // DisplayName
 56             // DisplayAttribute has precedence over DisplayNameAttribute.
 57             if (displayAttribute?.GetName() == null)
 58             {
 59                 if (displayNameAttribute != null)
 60                 {
 61                     if (localizer != null &&
 62                         !string.IsNullOrEmpty(displayNameAttribute.DisplayName))
 63                     {
 64                         displayMetadata.DisplayName = () => localizer[displayNameAttribute.DisplayName];
 65                     }
 66                     else
 67                     {
 68                         displayMetadata.DisplayName = () => displayNameAttribute.DisplayName;
 69                     }
 70                 }
 71             }
 72             else
 73             {
 74                 if (localizer != null &&
 75                     !string.IsNullOrEmpty(displayAttribute.Name) &&
 76                     displayAttribute.ResourceType == null)
 77                 {
 78                     displayMetadata.DisplayName = () => localizer[displayAttribute.Name];
 79                 }
 80                 else
 81                 {
 82                     displayMetadata.DisplayName = () => displayAttribute.GetName();
 83                 }
 84             }
 85 
 86             // EditFormatString
 87             if (displayFormatAttribute != null && displayFormatAttribute.ApplyFormatInEditMode)
 88             {
 89                 displayMetadata.EditFormatString = displayFormatAttribute.DataFormatString;
 90             }
 91 
 92             // IsEnum et cetera
 93             var underlyingType = Nullable.GetUnderlyingType(context.Key.ModelType) ?? context.Key.ModelType;
 94             var underlyingTypeInfo = underlyingType.GetTypeInfo();
 95 
 96             if (underlyingTypeInfo.IsEnum)
 97             {
 98                 // IsEnum
 99                 displayMetadata.IsEnum = true;
100 
101                 // IsFlagsEnum
102                 displayMetadata.IsFlagsEnum = underlyingTypeInfo.IsDefined(typeof(FlagsAttribute), inherit: false);
103 
104                 // EnumDisplayNamesAndValues and EnumNamesAndValues
105                 //
106                 // Order EnumDisplayNamesAndValues by DisplayAttribute.Order, then by the order of Enum.GetNames().
107                 // That method orders by absolute value, then its behavior is undefined (but hopefully stable).
108                 // Add to EnumNamesAndValues in same order but Dictionary does not guarantee order will be preserved.
109 
110                 var groupedDisplayNamesAndValues = new List<KeyValuePair<EnumGroupAndName, string>>();
111                 var namesAndValues = new Dictionary<string, string>();
112 
113                 IStringLocalizer enumLocalizer = null;
114                 if (_localizationOptions.AllowDataAnnotationsLocalizationForEnumDisplayAttributes)
115                 {
116                     if (_stringLocalizerFactory != null && _localizationOptions.DataAnnotationLocalizerProvider != null)
117                     {
118                         enumLocalizer = _localizationOptions.DataAnnotationLocalizerProvider(underlyingType, _stringLocalizerFactory);
119                     }
120                 }
121                 else
122                 {
123                     enumLocalizer = _stringLocalizerFactory?.Create(underlyingType);
124                 }
125 
126                 var enumFields = Enum.GetNames(underlyingType)
127                     .Select(name => underlyingType.GetField(name))
128                     .OrderBy(field => field.GetCustomAttribute<DisplayAttribute>(inherit: false)?.GetOrder() ?? 1000);
129 
130                 foreach (var field in enumFields)
131                 {
132                     var groupName = GetDisplayGroup(field);
133                     var value = ((Enum)field.GetValue(obj: null)).ToString("d");
134 
135                     groupedDisplayNamesAndValues.Add(new KeyValuePair<EnumGroupAndName, string>(
136                         new EnumGroupAndName(
137                             groupName,
138                             () => GetDisplayName(field, enumLocalizer)),
139                         value));
140                     namesAndValues.Add(field.Name, value);
141                 }
142 
143                 displayMetadata.EnumGroupedDisplayNamesAndValues = groupedDisplayNamesAndValues;
144                 displayMetadata.EnumNamesAndValues = namesAndValues;
145             }
146 
147             // HasNonDefaultEditFormat
148             if (!string.IsNullOrEmpty(displayFormatAttribute?.DataFormatString) &&
149                 displayFormatAttribute?.ApplyFormatInEditMode == true)
150             {
151                 // Have a non-empty EditFormatString based on [DisplayFormat] from our cache.
152                 if (dataTypeAttribute == null)
153                 {
154                     // Attributes include no [DataType]; [DisplayFormat] was applied directly.
155                     displayMetadata.HasNonDefaultEditFormat = true;
156                 }
157                 else if (dataTypeAttribute.DisplayFormat != displayFormatAttribute)
158                 {
159                     // Attributes include separate [DataType] and [DisplayFormat]; [DisplayFormat] provided override.
160                     displayMetadata.HasNonDefaultEditFormat = true;
161                 }
162                 else if (dataTypeAttribute.GetType() != typeof(DataTypeAttribute))
163                 {
164                     // Attributes include [DisplayFormat] copied from [DataType] and [DataType] was of a subclass.
165                     // Assume the [DataType] constructor used the protected DisplayFormat setter to override its
166                     // default.  That is derived [DataType] provided override.
167                     displayMetadata.HasNonDefaultEditFormat = true;
168                 }
169             }
170 
171             // HideSurroundingHtml
172             if (hiddenInputAttribute != null)
173             {
174                 displayMetadata.HideSurroundingHtml = !hiddenInputAttribute.DisplayValue;
175             }
176 
177             // HtmlEncode
178             if (displayFormatAttribute != null)
179             {
180                 displayMetadata.HtmlEncode = displayFormatAttribute.HtmlEncode;
181             }
182 
183             // NullDisplayText
184             if (displayFormatAttribute != null)
185             {
186                 displayMetadata.NullDisplayText = displayFormatAttribute.NullDisplayText;
187             }
188 
189             // Order
190             if (displayAttribute?.GetOrder() != null)
191             {
192                 displayMetadata.Order = displayAttribute.GetOrder().Value;
193             }
194 
195             // Placeholder
196             if (displayAttribute != null)
197             {
198                 if (localizer != null &&
199                     !string.IsNullOrEmpty(displayAttribute.Prompt) &&
200                     displayAttribute.ResourceType == null)
201                 {
202                     displayMetadata.Placeholder = () => localizer[displayAttribute.Prompt];
203                 }
204                 else
205                 {
206                     displayMetadata.Placeholder = () => displayAttribute.GetPrompt();
207                 }
208             }

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原文地址：https://www.cnblogs.com/SpeakHero/p/9639676.html