最近在專案中需要把各個欄位的釋義寫到資料庫中，該專案已經上線很長時間了，資料庫中的欄位沒有上千也有上百個，要是一個專案一個專案開啟然後再去找對應欄位檢視什麼意思，估計要到明年過年了。由於專案中使用EntityFramework，本身這個專案只有手動設定欄位註釋的功能，Coder平時寫程式碼的時候都懶得寫註釋，更別提能在配置資料庫的時候將註釋配置進去，所以如何在EF中自動將實體註釋寫入資料庫，減輕Coder的壓力（ru he tou lan）尤為重要。gitee地址：https://gitee.com/lbqman/Blog20210206.git 。下面進入正題。
一、實現思路
在FluentAPI中提供了HasComment方法，如下
11
1
/// <summary>Configures a comment to be applied to the column</summary>
2
/// <typeparam name="TProperty"> The type of the property being configured. </typeparam>
3
/// <param name="propertyBuilder"> The builder for the property being configured. </param>
4
/// <param name="comment"> The comment for the column. </param>
5
/// <returns> The same builder instance so that multiple calls can be chained. </returns>
6
public static PropertyBuilder<TProperty> HasComment<TProperty>(
7
[NotNull] this PropertyBuilder<TProperty> propertyBuilder,
8
[CanBeNull] string comment)
9
{
10
return (PropertyBuilder<TProperty>) propertyBuilder.HasComment(comment);
11
}
也就是說我們要獲取到實體物件的註釋xml，然後讀取對應的欄位註釋，自動呼叫改方法即可。需要解決的問題大概有以下幾點。
- 如何獲取當前配置的欄位；
- 載入Xml，並根據欄位獲取對應的註釋；
- 如何將列舉的各項資訊都放入註釋中；
二、實現方法
1.如何獲取當前配置的欄位
在獲取xml的註釋中，需要的資訊有實體對應的型別以及對應的欄位。而包含這兩種型別的方法只有Property這個方法，該方法的出入參如下：
2
1
public virtual PropertyBuilder<TProperty> Property<TProperty>(
2
[NotNull] Expression<Func<TEntity, TProperty>> propertyExpression);
所以我們準備對這個方法進行改造。並且根據傳入的propertyExpression獲取欄位名稱。方法如下：
4
1
public static PropertyBuilder<TProperty> SummaryProperty<TEntity, TProperty>(
2
this EntityTypeBuilder<TEntity> entityTypeBuilder,
3
Expression<Func<TEntity, TProperty>> propertyExpression)
4
where TEntity : class
根據表示式獲取欄位名稱如下：
10
1
public static MemberInfo GetMember<T, TProperty>(this Expression<Func<T, TProperty>> expression)
2
{
3
MemberExpression memberExp;
4
if (expression.Body is UnaryExpression unaryExpression)
5
memberExp = unaryExpression.Operand as MemberExpression;
6
else
7
memberExp = expression.Body as MemberExpression;
8
9
return memberExp?.Member;
10
}
2.載入Xml，並根據欄位獲取對應的註釋
VS中的Xml格式不在此處過多解釋，屬性、方法等註釋可以根據規律去獲取。此處需要注意的是當欄位是從父類繼承而來並且父類屬於不同的dll時，需要獲取父類所在dll的xml註釋才行，另外列舉也需要同樣去處理。雖然獲取Xml資料的方法只在更新資料庫時才呼叫，但是還是需要使用字典將資料快取下來，方便下次快速獲取。具體程式碼如下：
204
1
/// <summary>
2
/// xml註釋獲取器
3
/// </summary>
4
internal static class SummaryXmlCacheProvider
5
{
6
#region TClass
7
8
/// <summary>
9
/// 根據型別初始化該類所在程式集的xml
10
/// </summary>
11
/// <typeparam name="TClass"></typeparam>
12
internal static void InitSummaryXml<TClass>()
13
{
14
var assembly = Assembly.GetAssembly(typeof(TClass));
15
SerializeXmlFromAssembly(assembly);
16
}
17
18
/// <summary>
19
/// 根據型別獲取該類所在程式集的xml
20
/// </summary>
21
/// <typeparam name="TClass"></typeparam>
22
/// <returns></returns>
23
internal static Dictionary<string, string> GetSummaryXml<TClass>()
24
{
25
var assembly = Assembly.GetAssembly(typeof(TClass));
26
return SummaryCache[assembly];
27
}
28
29
/// <summary>
30
/// 獲取該類在xml的key
31
/// </summary>
32
/// <typeparam name="TClass"></typeparam>
33
/// <returns></returns>
34
internal static string GetClassTypeKey<TClass>()
35
{
36
return TableSummaryRuleProvider.TypeSummaryKey(typeof(TClass).FullName);
37
}
38
39
#endregion
40
41
#region TProperty
42
43
/// <summary>
44
/// 根據型別以及欄位初始化該類所在程式集的xml
45
/// </summary>
46
/// <typeparam name="TClass"></typeparam>
47
/// <typeparam name="TProperty"></typeparam>
48
/// <param name="propertyExpression"></param>
49
internal static void InitSummaryXml<TClass, TProperty>(Expression<Func<TClass, TProperty>> propertyExpression)
50
{
51
var propertyAssembly = GetPropertyAssembly(propertyExpression);
52
SerializeXmlFromAssembly(propertyAssembly);
53
}
54
55
/// <summary>
56
/// 根據型別以及欄位獲取該類所在程式集的xml
57
/// </summary>
58
/// <typeparam name="TClass"></typeparam>
59
/// <typeparam name="TProperty"></typeparam>
60
/// <param name="propertyExpression"></param>
61
/// <returns></returns>
62
internal static Dictionary<string, string> GetSummaryXml<TClass, TProperty>(
63
Expression<Func<TClass, TProperty>> propertyExpression)
64
{
65
var propertyAssembly = GetPropertyAssembly(propertyExpression);
66
return SummaryCache[propertyAssembly];
67
}
68
69
/// <summary>
70
/// 獲取該類以及欄位所在xml的key
71
/// </summary>
72
/// <typeparam name="TClass"></typeparam>
73
/// <typeparam name="TProperty"></typeparam>
74
/// <param name="propertyExpression"></param>
75
/// <returns></returns>
76
internal static string GetPropertyTypeKey<TClass, TProperty>(
77
Expression<Func<TClass, TProperty>> propertyExpression)
78
{
79
var memberName = propertyExpression.GetMember().Name;
80
var propertyInfo = GetPropertyInfo(propertyExpression);
81
var propertyKey =
82
$"{propertyInfo.DeclaringType.Namespace}.{propertyInfo.DeclaringType.Name}.{memberName}";
83
return PropertySummaryRuleProvider.PropertyTypeSummaryKey(propertyKey);
84
}
85
86
#endregion
87
88
#region TEnum
89
90
/// <summary>
91
/// 獲取列舉欄位的描述資訊
92
/// </summary>
93
/// <typeparam name="TClass"></typeparam>
94
/// <typeparam name="TProperty"></typeparam>
95
/// <param name="propertyExpression"></param>
96
/// <returns></returns>
97
internal static string GetEnumPropertyDescription<TClass, TProperty>(Expression<Func<TClass, TProperty>> propertyExpression)
98
{
99
var propertyInfo = GetPropertyInfo(propertyExpression);
100
if (!propertyInfo.PropertyType.IsEnum)
101
return string.Empty;
102
var enumType = propertyInfo.PropertyType;
103
SerializeXmlFromAssembly(enumType.Assembly);
104
var propertySummaryDic = SummaryCache[enumType.Assembly];
105
var enumNames = enumType.GetEnumNames();
106
var enumDescDic = enumType.GetNameAndValues();
107
var enumSummaries = new List<string>();
108
foreach (var enumName in enumNames)
109
{
110
var propertyEnumKey = PropertySummaryRuleProvider.EnumTypeSummaryKey($"{enumType.FullName}.{enumName}");
111
var enumSummary = propertySummaryDic.ContainsKey(propertyEnumKey)
112
? propertySummaryDic[propertyEnumKey]
113
: string.Empty;
114
var enumValue = enumDescDic[enumName];
115
enumSummaries.Add(PropertySummaryRuleProvider.EnumTypeSummaryFormat(enumValue,enumName,enumSummary));
116
}
117
118
return string.Join(";", enumSummaries);
119
120
}
121
122
#endregion
123
124
/// <summary>
125
/// 根據表示式獲取屬性所在的程式集
126
/// </summary>
127
/// <typeparam name="TClass"></typeparam>
128
/// <typeparam name="TProperty"></typeparam>
129
/// <param name="propertyExpression"></param>
130
/// <returns></returns>
131
private static Assembly GetPropertyAssembly<TClass, TProperty>(
132
Expression<Func<TClass, TProperty>> propertyExpression)
133
{
134
var propertyInfo = GetPropertyInfo(propertyExpression);
135
var propertyAssembly = propertyInfo.Module.Assembly;
136
return propertyAssembly;
137
}
138
139
/// <summary>
140
/// 根據表示式獲取欄位屬性
141
/// </summary>
142
/// <typeparam name="TClass"></typeparam>
143
/// <typeparam name="TProperty"></typeparam>
144
/// <param name="propertyExpression"></param>
145
/// <returns></returns>
146
private static PropertyInfo GetPropertyInfo<TClass, TProperty>(
147
Expression<Func<TClass, TProperty>> propertyExpression)
148
{
149
var entityType = typeof(TClass);
150
var memberName = propertyExpression.GetMember().Name;
151
var propertyInfo = entityType.GetProperty(memberName, typeof(TProperty));
152
if (propertyInfo == null || propertyInfo.DeclaringType == null)
153
throw new ArgumentNullException($"this property {memberName} is not belong to {entityType.Name}");
154
155
return propertyInfo;
156
}
157
158
/// <summary>
159
/// 根據程式集初始化xml
160
/// </summary>
161
/// <param name="assembly"></param>
162
private static void SerializeXmlFromAssembly(Assembly assembly)
163
{
164
var assemblyPath = assembly.Location;
165
var lastIndexOf = assemblyPath.LastIndexOf(".dll", StringComparison.Ordinal);
166
var xmlPath = assemblyPath.Remove(lastIndexOf, 4) + ".xml";
167
168
if (SummaryCache.ContainsKey(assembly))
169
return;
170
var xmlDic = new Dictionary<string, string>();
171
if (!File.Exists(xmlPath))
172
{
173
Console.WriteLine($"未能載入xml檔案，原因：xml檔案不存在，path：{xmlPath}");
174
SummaryCache.Add(assembly, xmlDic);
175
return;
176
}
177
178
var doc = new XmlDocument();
179
doc.Load(xmlPath);
180
var members = doc.SelectNodes("doc/members/member");
181
if (members == null)
182
{
183
Console.WriteLine($"未能載入xml檔案，原因：doc/members/member節點不存在");
184
SummaryCache.Add(assembly, xmlDic);
185
return;
186
}
187
188
foreach (XmlElement member in members)
189
{
190
var name = member.Attributes["name"].InnerText.Trim();
191
if (string.IsNullOrWhiteSpace(name))
192
continue;
193
xmlDic.Add(name, member.SelectSingleNode("summary")?.InnerText.Trim());
194
}
195
196
SummaryCache.Add(assembly, xmlDic);
197
}
198
199
/// <summary>
200
/// xml註釋快取
201
/// </summary>
202
private static Dictionary<Assembly, Dictionary<string, string>> SummaryCache { get; } =
203
new Dictionary<Assembly, Dictionary<string, string>>();
204
}
3.如何將列舉的各項資訊都放入註釋中
上面的兩個步驟已經根據表示式將欄位的註釋獲取到，直接呼叫EF提供的HasComment即可。見程式碼：
15
1
public static PropertyBuilder<TProperty> SummaryProperty<TEntity, TProperty>(
2
this EntityTypeBuilder<TEntity> entityTypeBuilder,
3
Expression<Func<TEntity, TProperty>> propertyExpression)
4
where TEntity : class
5
{
6
SummaryXmlCacheProvider.InitSummaryXml(propertyExpression);
7
var entitySummaryDic = SummaryXmlCacheProvider.GetSummaryXml(propertyExpression);
8
var propertyKey = SummaryXmlCacheProvider.GetPropertyTypeKey(propertyExpression);
9
var summary = entitySummaryDic.ContainsKey(propertyKey) ? entitySummaryDic[propertyKey] : string.Empty;
10
var enumDescription = SummaryXmlCacheProvider.GetEnumPropertyDescription(propertyExpression);
11
summary = string.IsNullOrWhiteSpace(enumDescription) ? summary : $"{summary}：{enumDescription}";
12
return string.IsNullOrWhiteSpace(summary)
13
? entityTypeBuilder.Property(propertyExpression)
14
: entityTypeBuilder.Property(propertyExpression).HasComment(summary);
15
}
同時也可以設定表的註釋以及表的名稱。如下：
26
1
public static EntityTypeBuilder<TEntity> SummaryToTable<TEntity>(
2
this EntityTypeBuilder<TEntity> entityTypeBuilder, bool hasTableComment = true,
3
Func<string> tablePrefix = null)
4
where TEntity : class
5
{
6
var tableName = GetTableName<TEntity>(tablePrefix);
7
return hasTableComment
8
? entityTypeBuilder.ToTable(tableName)
9
.SummaryHasComment()
10
: entityTypeBuilder.ToTable(tableName);
11
}
12
13
public static EntityTypeBuilder<TEntity> SummaryHasComment<TEntity>(
14
this EntityTypeBuilder<TEntity> entityTypeBuilder) where TEntity : class
15
{
16
SummaryXmlCacheProvider.InitSummaryXml<TEntity>();
17
var entityDic = SummaryXmlCacheProvider.GetSummaryXml<TEntity>();
18
var tableKey = SummaryXmlCacheProvider.GetClassTypeKey<TEntity>();
19
var summary = entityDic.ContainsKey(tableKey) ? entityDic[tableKey] : string.Empty;
20
return string.IsNullOrWhiteSpace(summary) ? entityTypeBuilder : entityTypeBuilder.HasComment(summary);
21
}
22
23
private static string GetTableName<TEntity>(Func<string> tablePrefix)
24
{
25
return typeof(TEntity).Name.Replace("Entity", $"Tb{tablePrefix?.Invoke()}");
26
}
搞定。
三、效果展示
執行Add-Migration InitDb即可檢視生成的程式碼。
1
public partial class InitDb : Migration
2
{
3
protected override void Up(MigrationBuilder migrationBuilder)
4
{
5
migrationBuilder.CreateTable(
6
name: "TbGood",
7
columns: table => new
8
{
9
Id = table.Column<long>(nullable: false, comment: "主鍵")
10
.Annotation("SqlServer:Identity", "1, 1"),
11
CreateTime = table.Column<DateTime>(nullable: false, comment: "建立時間"),
12
CreateName = table.Column<string>(maxLength: 64, nullable: false, comment: "建立人姓名"),
13
UpdateTime = table.Column<DateTime>(nullable: true, comment: "更新時間"),
14
UpdateName = table.Column<string>(maxLength: 64, nullable: true, comment: "更新人姓名"),
15
Name = table.Column<string>(maxLength: 64, nullable: false, comment: "商品名稱"),
16
GoodType = table.Column<int>(nullable: false, comment: "物品型別：(0,Electronic) 電子產品;(1,Clothes) 衣帽服裝;(2,Food) 食品;(3,Other) 其他物品"),
17
Description = table.Column<string>(maxLength: 2048, nullable: true, comment: "物品描述"),
18
Store = table.Column<int>(nullable: false, comment: "儲存量")
19
},
20
constraints: table =>
21
{
22
table.PrimaryKey("PK_TbGood", x => x.Id);
23
},
24
comment: "商品實體類");
25
26
migrationBuilder.CreateTable(
27
name: "TbOrder",
28
columns: table => new
29
{
30
Id = table.Column<long>(nullable: false, comment: "主鍵")
31
.Annotation("SqlServer:Identity", "1, 1"),
32
CreateTime = table.Column<DateTime>(nullable: false, comment: "建立時間"),
33
CreateName = table.Column<string>(maxLength: 64, nullable: false, comment: "建立人姓名"),
34
UpdateTime = table.Column<DateTime>(nullable: true, comment: "更新時間"),
35
UpdateName = table.Column<string>(maxLength: 64, nullable: true, comment: "更新人姓名"),
36
GoodId = table.Column<long>(nullable: false, comment: "商品Id"),
37
OrderStatus = table.Column<int>(nullable: false, comment: "訂單狀態：(0,Ordered) 已下單;(1,Payed) 已付款;(2,Complete) 已付款;(3,Cancel) 已取消"),
38
OrderTime = table.Column<DateTime>(nullable: false, comment: "下訂單時間"),
39
Address = table.Column<string>(maxLength: 2048, nullable: false, comment: "訂單地址"),
40
UserName = table.Column<string>(maxLength: 16, nullable: false, comment: "收件人姓名"),
41
TotalAmount = table.Column<decimal>(nullable: false, comment: "總金額")
42
},
43
constraints: table =>
44
{
45
table.PrimaryKey("PK_TbOrder", x => x.Id);
46
},
47
comment: "訂單實體類");
48
}
49
50
protected override void Down(MigrationBuilder migrationBuilder)
51
{
52
migrationBuilder.DropTable(
53
name: "TbGood");
54
55
migrationBuilder.DropTable(
56
name: "TbOrder");
57
}
58
}
四、寫在最後
此種方法是在我目前能想起來比較方便生成註釋的方法了，另外還想過EntityTypeBuilder中的Property方法，最後還是放棄了，因為EntityTypeBuilder是由ModelBuilder生成，而ModelBuilder又是ModelSource中的CreateModel方法產生，最後一路深扒到DbContext中，為了搞這個註釋得不償失，最後才採取了上述的方法。若是大佬有更好的方法，恭請分享。