【繁星Code】如何在EF将实体注释写入数据库中
最近在项目中需要把各个字段的释义写到数据库中，该项目已经上线很长时间了，数据库中的字段没有上千也有上百个，要是一个项目一个项目打开然后再去找对应字段查看什么意思，估计要到明年过年了。由于项目中使用EntityFramework，本身这个项目只有手动设置字段注释的功能，Coder平时写代码的时候都懒得写注释，更别提能在配置数据库的时候将注释配置进去，所以如何在EF中自动将实体注释写入数据库，减轻Coder的压力（ru he tou lan）尤为重要。gitee地址：https://gitee.com/lbqman/Blog20210206.git 。下面进入正题。
一、实现思路
在FluentAPI中提供了HasComment方法，如下
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1
/// <summary>Configures a comment to be applied to the column</summary>
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/// <typeparam name="TProperty"> The type of the property being configured. </typeparam>
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/// <param name="propertyBuilder"> The builder for the property being configured. </param>
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/// <param name="comment"> The comment for the column. </param>
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/// <returns> The same builder instance so that multiple calls can be chained. </returns>
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public static PropertyBuilder<TProperty> HasComment<TProperty>(
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[NotNull] this PropertyBuilder<TProperty> propertyBuilder,
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[CanBeNull] string comment)
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{
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return (PropertyBuilder<TProperty>) propertyBuilder.HasComment(comment);
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}
也就是说我们要获取到实体对象的注释xml，然后读取对应的字段注释，自动调用改方法即可。需要解决的问题大概有以下几点。
- 如何获取当前配置的字段；
- 加载Xml，并根据字段获取对应的注释；
- 如何将枚举的各项信息都放入注释中；
二、实现方法
1.如何获取当前配置的字段
在获取xml的注释中，需要的信息有实体对应的类型以及对应的字段。而包含这两种类型的方法只有Property这个方法，该方法的出入参如下：
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1
public virtual PropertyBuilder<TProperty> Property<TProperty>(
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[NotNull] Expression<Func<TEntity, TProperty>> propertyExpression);
所以我们准备对这个方法进行改造。并且根据传入的propertyExpression获取字段名称。方法如下：
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1
public static PropertyBuilder<TProperty> SummaryProperty<TEntity, TProperty>(
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this EntityTypeBuilder<TEntity> entityTypeBuilder,
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Expression<Func<TEntity, TProperty>> propertyExpression)
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where TEntity : class
根据表达式获取字段名称如下：
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1
public static MemberInfo GetMember<T, TProperty>(this Expression<Func<T, TProperty>> expression)
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{
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MemberExpression memberExp;
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if (expression.Body is UnaryExpression unaryExpression)
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memberExp = unaryExpression.Operand as MemberExpression;
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else
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memberExp = expression.Body as MemberExpression;
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return memberExp?.Member;
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}
2.加载Xml，并根据字段获取对应的注释
VS中的Xml格式不在此处过多解释，属性、方法等注释可以根据规律去获取。此处需要注意的是当字段是从父类继承而来并且父类属于不同的dll时，需要获取父类所在dll的xml注释才行，另外枚举也需要同样去处理。虽然获取Xml数据的方法只在更新数据库时才调用，但是还是需要使用字典将数据缓存下来，方便下次快速获取。具体代码如下：
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1
/// <summary>
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/// xml注释获取器
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/// </summary>
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internal static class SummaryXmlCacheProvider
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{
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#region TClass
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/// <summary>
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/// 根据类型初始化该类所在程序集的xml
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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internal static void InitSummaryXml<TClass>()
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{
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var assembly = Assembly.GetAssembly(typeof(TClass));
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SerializeXmlFromAssembly(assembly);
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}
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/// <summary>
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/// 根据类型获取该类所在程序集的xml
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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/// <returns></returns>
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internal static Dictionary<string, string> GetSummaryXml<TClass>()
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{
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var assembly = Assembly.GetAssembly(typeof(TClass));
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return SummaryCache[assembly];
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}
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/// <summary>
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/// 获取该类在xml的key
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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/// <returns></returns>
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internal static string GetClassTypeKey<TClass>()
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{
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return TableSummaryRuleProvider.TypeSummaryKey(typeof(TClass).FullName);
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}
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#endregion
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#region TProperty
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/// <summary>
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/// 根据类型以及字段初始化该类所在程序集的xml
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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/// <typeparam name="TProperty"></typeparam>
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/// <param name="propertyExpression"></param>
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internal static void InitSummaryXml<TClass, TProperty>(Expression<Func<TClass, TProperty>> propertyExpression)
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{
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var propertyAssembly = GetPropertyAssembly(propertyExpression);
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SerializeXmlFromAssembly(propertyAssembly);
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}
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/// <summary>
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/// 根据类型以及字段获取该类所在程序集的xml
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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/// <typeparam name="TProperty"></typeparam>
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/// <param name="propertyExpression"></param>
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/// <returns></returns>
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internal static Dictionary<string, string> GetSummaryXml<TClass, TProperty>(
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Expression<Func<TClass, TProperty>> propertyExpression)
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{
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var propertyAssembly = GetPropertyAssembly(propertyExpression);
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return SummaryCache[propertyAssembly];
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}
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/// <summary>
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/// 获取该类以及字段所在xml的key
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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/// <typeparam name="TProperty"></typeparam>
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/// <param name="propertyExpression"></param>
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/// <returns></returns>
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internal static string GetPropertyTypeKey<TClass, TProperty>(
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Expression<Func<TClass, TProperty>> propertyExpression)
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{
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var memberName = propertyExpression.GetMember().Name;
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var propertyInfo = GetPropertyInfo(propertyExpression);
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var propertyKey =
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$"{propertyInfo.DeclaringType.Namespace}.{propertyInfo.DeclaringType.Name}.{memberName}";
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return PropertySummaryRuleProvider.PropertyTypeSummaryKey(propertyKey);
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}
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#endregion
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#region TEnum
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/// <summary>
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/// 获取枚举字段的描述信息
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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/// <typeparam name="TProperty"></typeparam>
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/// <param name="propertyExpression"></param>
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/// <returns></returns>
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internal static string GetEnumPropertyDescription<TClass, TProperty>(Expression<Func<TClass, TProperty>> propertyExpression)
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{
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var propertyInfo = GetPropertyInfo(propertyExpression);
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if (!propertyInfo.PropertyType.IsEnum)
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return string.Empty;
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var enumType = propertyInfo.PropertyType;
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SerializeXmlFromAssembly(enumType.Assembly);
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var propertySummaryDic = SummaryCache[enumType.Assembly];
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var enumNames = enumType.GetEnumNames();
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var enumDescDic = enumType.GetNameAndValues();
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var enumSummaries = new List<string>();
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foreach (var enumName in enumNames)
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{
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var propertyEnumKey = PropertySummaryRuleProvider.EnumTypeSummaryKey($"{enumType.FullName}.{enumName}");
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var enumSummary = propertySummaryDic.ContainsKey(propertyEnumKey)
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? propertySummaryDic[propertyEnumKey]
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: string.Empty;
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var enumValue = enumDescDic[enumName];
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enumSummaries.Add(PropertySummaryRuleProvider.EnumTypeSummaryFormat(enumValue,enumName,enumSummary));
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}
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return string.Join(";", enumSummaries);
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}
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#endregion
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/// <summary>
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/// 根据表达式获取属性所在的程序集
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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/// <typeparam name="TProperty"></typeparam>
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/// <param name="propertyExpression"></param>
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/// <returns></returns>
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private static Assembly GetPropertyAssembly<TClass, TProperty>(
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Expression<Func<TClass, TProperty>> propertyExpression)
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{
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var propertyInfo = GetPropertyInfo(propertyExpression);
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var propertyAssembly = propertyInfo.Module.Assembly;
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return propertyAssembly;
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}
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/// <summary>
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/// 根据表达式获取字段属性
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/// </summary>
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/// <typeparam name="TClass"></typeparam>
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/// <typeparam name="TProperty"></typeparam>
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/// <param name="propertyExpression"></param>
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/// <returns></returns>
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private static PropertyInfo GetPropertyInfo<TClass, TProperty>(
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Expression<Func<TClass, TProperty>> propertyExpression)
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{
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var entityType = typeof(TClass);
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var memberName = propertyExpression.GetMember().Name;
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var propertyInfo = entityType.GetProperty(memberName, typeof(TProperty));
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if (propertyInfo == null || propertyInfo.DeclaringType == null)
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throw new ArgumentNullException($"this property {memberName} is not belong to {entityType.Name}");
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return propertyInfo;
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}
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/// <summary>
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/// 根据程序集初始化xml
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/// </summary>
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/// <param name="assembly"></param>
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private static void SerializeXmlFromAssembly(Assembly assembly)
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{
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var assemblyPath = assembly.Location;
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var lastIndexOf = assemblyPath.LastIndexOf(".dll", StringComparison.Ordinal);
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var xmlPath = assemblyPath.Remove(lastIndexOf, 4) + ".xml";
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if (SummaryCache.ContainsKey(assembly))
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return;
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var xmlDic = new Dictionary<string, string>();
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if (!File.Exists(xmlPath))
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{
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Console.WriteLine($"未能加载xml文件，原因：xml文件不存在，path：{xmlPath}");
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SummaryCache.Add(assembly, xmlDic);
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return;
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}
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var doc = new XmlDocument();
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doc.Load(xmlPath);
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var members = doc.SelectNodes("doc/members/member");
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if (members == null)
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{
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Console.WriteLine($"未能加载xml文件，原因：doc/members/member节点不存在");
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SummaryCache.Add(assembly, xmlDic);
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return;
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}
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foreach (XmlElement member in members)
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{
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var name = member.Attributes["name"].InnerText.Trim();
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if (string.IsNullOrWhiteSpace(name))
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continue;
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xmlDic.Add(name, member.SelectSingleNode("summary")?.InnerText.Trim());
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}
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SummaryCache.Add(assembly, xmlDic);
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}
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/// <summary>
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/// xml注释缓存
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/// </summary>
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private static Dictionary<Assembly, Dictionary<string, string>> SummaryCache { get; } =
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new Dictionary<Assembly, Dictionary<string, string>>();
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}
3.如何将枚举的各项信息都放入注释中
上面的两个步骤已经根据表达式将字段的注释获取到，直接调用EF提供的HasComment即可。见代码：
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public static PropertyBuilder<TProperty> SummaryProperty<TEntity, TProperty>(
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this EntityTypeBuilder<TEntity> entityTypeBuilder,
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Expression<Func<TEntity, TProperty>> propertyExpression)
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where TEntity : class
5
{
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SummaryXmlCacheProvider.InitSummaryXml(propertyExpression);
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var entitySummaryDic = SummaryXmlCacheProvider.GetSummaryXml(propertyExpression);
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var propertyKey = SummaryXmlCacheProvider.GetPropertyTypeKey(propertyExpression);
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var summary = entitySummaryDic.ContainsKey(propertyKey) ? entitySummaryDic[propertyKey] : string.Empty;
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var enumDescription = SummaryXmlCacheProvider.GetEnumPropertyDescription(propertyExpression);
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summary = string.IsNullOrWhiteSpace(enumDescription) ? summary : $"{summary}：{enumDescription}";
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return string.IsNullOrWhiteSpace(summary)
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? entityTypeBuilder.Property(propertyExpression)
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: entityTypeBuilder.Property(propertyExpression).HasComment(summary);
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}
同时也可以设置表的注释以及表的名称。如下：
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1
public static EntityTypeBuilder<TEntity> SummaryToTable<TEntity>(
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this EntityTypeBuilder<TEntity> entityTypeBuilder, bool hasTableComment = true,
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Func<string> tablePrefix = null)
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where TEntity : class
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{
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var tableName = GetTableName<TEntity>(tablePrefix);
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return hasTableComment
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? entityTypeBuilder.ToTable(tableName)
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.SummaryHasComment()
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: entityTypeBuilder.ToTable(tableName);
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}
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13
public static EntityTypeBuilder<TEntity> SummaryHasComment<TEntity>(
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this EntityTypeBuilder<TEntity> entityTypeBuilder) where TEntity : class
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{
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SummaryXmlCacheProvider.InitSummaryXml<TEntity>();
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var entityDic = SummaryXmlCacheProvider.GetSummaryXml<TEntity>();
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var tableKey = SummaryXmlCacheProvider.GetClassTypeKey<TEntity>();
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var summary = entityDic.ContainsKey(tableKey) ? entityDic[tableKey] : string.Empty;
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return string.IsNullOrWhiteSpace(summary) ? entityTypeBuilder : entityTypeBuilder.HasComment(summary);
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}
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private static string GetTableName<TEntity>(Func<string> tablePrefix)
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{
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return typeof(TEntity).Name.Replace("Entity", $"Tb{tablePrefix?.Invoke()}");
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}
搞定。
三、效果展示
运行Add-Migration InitDb即可查看生成的代码。
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public partial class InitDb : Migration
2
{
3
protected override void Up(MigrationBuilder migrationBuilder)
4
{
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migrationBuilder.CreateTable(
6
name: "TbGood",
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columns: table => new
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{
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Id = table.Column<long>(nullable: false, comment: "主键")
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.Annotation("SqlServer:Identity", "1, 1"),
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CreateTime = table.Column<DateTime>(nullable: false, comment: "创建时间"),
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CreateName = table.Column<string>(maxLength: 64, nullable: false, comment: "创建人姓名"),
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UpdateTime = table.Column<DateTime>(nullable: true, comment: "更新时间"),
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UpdateName = table.Column<string>(maxLength: 64, nullable: true, comment: "更新人姓名"),
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Name = table.Column<string>(maxLength: 64, nullable: false, comment: "商品名称"),
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GoodType = table.Column<int>(nullable: false, comment: "物品类型：(0,Electronic) 电子产品;(1,Clothes) 衣帽服装;(2,Food) 食品;(3,Other) 其他物品"),
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Description = table.Column<string>(maxLength: 2048, nullable: true, comment: "物品描述"),
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Store = table.Column<int>(nullable: false, comment: "储存量")
19
},
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constraints: table =>
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{
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table.PrimaryKey("PK_TbGood", x => x.Id);
23
},
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comment: "商品实体类");
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migrationBuilder.CreateTable(
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name: "TbOrder",
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columns: table => new
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{
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Id = table.Column<long>(nullable: false, comment: "主键")
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.Annotation("SqlServer:Identity", "1, 1"),
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CreateTime = table.Column<DateTime>(nullable: false, comment: "创建时间"),
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CreateName = table.Column<string>(maxLength: 64, nullable: false, comment: "创建人姓名"),
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UpdateTime = table.Column<DateTime>(nullable: true, comment: "更新时间"),
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UpdateName = table.Column<string>(maxLength: 64, nullable: true, comment: "更新人姓名"),
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GoodId = table.Column<long>(nullable: false, comment: "商品Id"),
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OrderStatus = table.Column<int>(nullable: false, comment: "订单状态：(0,Ordered) 已下单;(1,Payed) 已付款;(2,Complete) 已付款;(3,Cancel) 已取消"),
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OrderTime = table.Column<DateTime>(nullable: false, comment: "下订单时间"),
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Address = table.Column<string>(maxLength: 2048, nullable: false, comment: "订单地址"),
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UserName = table.Column<string>(maxLength: 16, nullable: false, comment: "收件人姓名"),
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TotalAmount = table.Column<decimal>(nullable: false, comment: "总金额")
42
},
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constraints: table =>
44
{
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table.PrimaryKey("PK_TbOrder", x => x.Id);
46
},
47
comment: "订单实体类");
48
}
49
50
protected override void Down(MigrationBuilder migrationBuilder)
51
{
52
migrationBuilder.DropTable(
53
name: "TbGood");
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55
migrationBuilder.DropTable(
56
name: "TbOrder");
57
}
58
}
四、写在最后
此种方法是在我目前能想起来比较方便生成注释的方法了，另外还想过EntityTypeBuilder中的Property方法，最后还是放弃了，因为EntityTypeBuilder是由ModelBuilder生成，而ModelBuilder又是ModelSource中的CreateModel方法产生，最后一路深扒到DbContext中，为了搞这个注释得不偿失，最后才采取了上述的方法。若是大佬有更好的方法，恭请分享。
