DbMigration类的扩展方法，将sp_updateextendedproperty或sp_addextendedproperty过程调用注册为迁移事务内的SQL迁移操作，并在迁移Up方法中的表创建后调用该扩展方法。但是否有一种优雅的内置方式我还没有发现？希望有一个属性，迁移的更改检测逻辑可以捕捉到并在生成的迁移中生成相应的方法调用。我也需要这个。所以我花了一天时间，现在给大家分享：
代码
public class DbDescriptionUpdater<TContext>
where TContext : System.Data.Entity.DbContext
{
public DbDescriptionUpdater(TContext context)
{
this.context = context;
}
Type contextType;
TContext context;
DbTransaction transaction;
public void UpdateDatabaseDescriptions()
{
contextType = typeof(TContext);
this.context = context;
var props = contextType.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
transaction = null;
try
{
context.Database.Connection.Open();
transaction = context.Database.Connection.BeginTransaction();
foreach (var prop in props)
{
if (prop.PropertyType.InheritsOrImplements((typeof(DbSet<>))))
{
var tableType = prop.PropertyType.GetGenericArguments()[0];
SetTableDescriptions(tableType);
}
}
transaction.Commit();
}
catch
{
if (transaction != null)
transaction.Rollback();
throw;
}
finally
{
if (context.Database.Connection.State == System.Data.ConnectionState.Open)
context.Database.Connection.Close();
}
}
private void SetTableDescriptions(Type tableType)
{
string fullTableName = context.GetTableName(tableType);
Regex regex = new Regex(@"(\[\w+\]\.)?\[(?<table>.*)\]");
Match match = regex.Match(fullTableName);
string tableName;
if (match.Success)
tableName = match.Groups["table"].Value;
else
tableName = fullTableName;
var tableAttrs = tableType.GetCustomAttributes(typeof(TableAttribute), false);
if (tableAttrs.Length > 0)
tableName = ((TableAttribute)tableAttrs[0]).Name;
foreach (var prop in tableType.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
{
if (prop.PropertyType.IsClass && prop.PropertyType != typeof(string))
continue;
var attrs = prop.GetCustomAttributes(typeof(DisplayAttribute), false);
if (attrs.Length > 0)
SetColumnDescription(tableName, prop.Name, ((DisplayAttribute)attrs[0]).Name);
}
}
private void SetColumnDescription(string tableName, string columnName, string description)
{
string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "','column',null) where objname = N'" + columnName + "';";
var prevDesc = RunSqlScalar(strGetDesc);
if (prevDesc == null)
{
RunSql(@"EXEC sp_addextendedproperty
@name = N'MS_Description', @value = @desc,
@level0type = N'Schema', @level0name = 'dbo',
@level1type = N'Table', @level1name = @table,
@level2type = N'Column', @level2name = @column;",
new SqlParameter("@table", tableName),
new SqlParameter("@column", columnName),
new SqlParameter("@desc", description));
}
else
{
RunSql(@"EXEC sp_updateextendedproperty
@name = N'MS_Description', @value = @desc,
@level0type = N'Schema', @level0name = 'dbo',
@level1type = N'Table', @level1name = @table,
@level2type = N'Column', @level2name = @column;",
new SqlParameter("@table", tableName),
new SqlParameter("@column", columnName),
new SqlParameter("@desc", description));
}
}
DbCommand CreateCommand(string cmdText, params SqlParameter[] parameters)
{
var cmd = context.Database.Connection.CreateCommand();
cmd.CommandText = cmdText;
cmd.Transaction = transaction;
foreach (var p in parameters)
cmd.Parameters.Add(p);
return cmd;
}
void RunSql(string cmdText, params SqlParameter[] parameters)
{
var cmd = CreateCommand(cmdText, parameters);
cmd.ExecuteNonQuery();
}
object RunSqlScalar(string cmdText, params SqlParameter[] parameters)
{
var cmd = CreateCommand(cmdText, parameters);
return cmd.ExecuteScalar();
}
}
public static class ReflectionUtil
{
public static bool InheritsOrImplements(this Type child, Type parent)
{
parent = ResolveGenericTypeDefinition(parent);
var currentChild = child.IsGenericType
? child.GetGenericTypeDefinition()
: child;
while (currentChild != typeof(object))
{
if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
return true;
currentChild = currentChild.BaseType != null
&& currentChild.BaseType.IsGenericType
? currentChild.BaseType.GetGenericTypeDefinition()
: currentChild.BaseType;
if (currentChild == null)
return false;
}
return false;
}
private static bool HasAnyInterfaces(Type parent, Type child)
{
return child.GetInterfaces()
.Any(childInterface =>
{
var currentInterface = childInterface.IsGenericType
? childInterface.GetGenericTypeDefinition()
: childInterface;
return currentInterface == parent;
});
}
private static Type ResolveGenericTypeDefinition(Type parent)
{
var shouldUseGenericType = true;
if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
shouldUseGenericType = false;
if (parent.IsGenericType && shouldUseGenericType)
parent = parent.GetGenericTypeDefinition();
return parent;
}
}
public static class ContextExtensions
{
public static string GetTableName(this DbContext context, Type tableType)
{
MethodInfo method = typeof(ContextExtensions).GetMethod("GetTableName", new Type[] { typeof(DbContext) })
.MakeGenericMethod(new Type[] { tableType });
return (string)method.Invoke(context, new object[] { context });
}
public static string GetTableName<T>(this DbContext context) where T : class
{
ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;
return objectContext.GetTableName<T>();
}
public static string GetTableName<T>(this ObjectContext context) where T : class
{
string sql = context.CreateObjectSet<T>().ToTraceString();
Regex regex = new Regex("FROM (?<table>.*) AS");
Match match = regex.Match(sql);
string table = match.Groups["table"].Value;
return table;
}
}
如何使用
在你的 Migrations/Configuration.cs 文件中，在 Seed 方法的结尾添加以下内容：
DbDescriptionUpdater<ContextClass> updater = new DbDescriptionUpdater<ContextClass>(context);
updater.UpdateDatabaseDescriptions();
然后在程序包管理器控制台中键入update-database并按Enter键。
该代码使用实体类属性上的[Display(Name="Description here")]属性来设置描述。
请报告任何错误或建议改进。
感谢
我使用了其他人的代码，我想说声谢谢：
public virtual string Description
{
get { return _description; }
set { _description = value; }
}} - gnome虽然对当前的回答还不太满意（但是对于这项工作还是要表扬！），我想寻找一种在我的类中提取现有注释标记的方法，而不是使用属性。我认为微软为什么不支持这个功能我实在是不明白，因为它显然应该存在！
首先，打开XML文档：项目属性->生成->XML文档文件->App_Data\YourProjectName.XML
其次，将该文件包含为嵌入式资源。构建项目，进入App_Data，显示隐藏文件并包含生成的XML文件。选择“嵌入式资源”和“如果更新则复制”（这是可选的，您也可以显式指定路径，但我认为这样更清晰）。请注意，必须使用此方法，因为标记不会出现在程序集中，并且这将使您免于查找XML存储位置的麻烦。
下面是代码实现，这是被接受回答的修改版本：
public class SchemaDescriptionUpdater<TContext> where TContext : DbContext
{
Type contextType;
TContext context;
DbTransaction transaction;
XmlAnnotationReader reader;
public SchemaDescriptionUpdater(TContext context)
{
this.context = context;
reader = new XmlAnnotationReader();
}
public SchemaDescriptionUpdater(TContext context, string xmlDocumentationPath)
{
this.context = context;
reader = new XmlAnnotationReader(xmlDocumentationPath);
}
public void UpdateDatabaseDescriptions()
{
contextType = typeof(TContext);
var props = contextType.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
transaction = null;
try
{
context.Database.Connection.Open();
transaction = context.Database.Connection.BeginTransaction();
foreach (var prop in props)
{
if (prop.PropertyType.InheritsOrImplements((typeof(DbSet<>))))
{
var tableType = prop.PropertyType.GetGenericArguments()[0];
SetTableDescriptions(tableType);
}
}
transaction.Commit();
}
catch
{
if (transaction != null)
transaction.Rollback();
throw;
}
finally
{
if (context.Database.Connection.State == System.Data.ConnectionState.Open)
context.Database.Connection.Close();
}
}
private void SetTableDescriptions(Type tableType)
{
string fullTableName = context.GetTableName(tableType);
Regex regex = new Regex(@"(\[\w+\]\.)?\[(?<table>.*)\]");
Match match = regex.Match(fullTableName);
string tableName;
if (match.Success)
tableName = match.Groups["table"].Value;
else
tableName = fullTableName;
var tableAttrs = tableType.GetCustomAttributes(typeof(TableAttribute), false);
if (tableAttrs.Length > 0)
tableName = ((TableAttribute)tableAttrs[0]).Name;
// set the description for the table
string tableComment = reader.GetCommentsForResource(tableType, null, XmlResourceType.Type);
if (!string.IsNullOrEmpty(tableComment))
SetDescriptionForObject(tableName, null, tableComment);
// get all of the documentation for each property/column
ObjectDocumentation[] columnComments = reader.GetCommentsForResource(tableType);
foreach (var column in columnComments)
{
SetDescriptionForObject(tableName, column.PropertyName, column.Documentation);
}
}
private void SetDescriptionForObject(string tableName, string columnName, string description)
{
string strGetDesc = "";
// determine if there is already an extended description
if(string.IsNullOrEmpty(columnName))
strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "',null,null);";
else
strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "','column',null) where objname = N'" + columnName + "';";
var prevDesc = (string)RunSqlScalar(strGetDesc);
var parameters = new List<SqlParameter>
{
new SqlParameter("@table", tableName),
new SqlParameter("@desc", description)
};
// is it an update, or new?
string funcName = "sp_addextendedproperty";
if (!string.IsNullOrEmpty(prevDesc))
funcName = "sp_updateextendedproperty";
string query = @"EXEC " + funcName + @" @name = N'MS_Description', @value = @desc,@level0type = N'Schema', @level0name = 'dbo',@level1type = N'Table', @level1name = @table";
// if a column is specified, add a column description
if (!string.IsNullOrEmpty(columnName))
{
parameters.Add(new SqlParameter("@column", columnName));
query += ", @level2type = N'Column', @level2name = @column";
}
RunSql(query, parameters.ToArray());
}
DbCommand CreateCommand(string cmdText, params SqlParameter[] parameters)
{
var cmd = context.Database.Connection.CreateCommand();
cmd.CommandText = cmdText;
cmd.Transaction = transaction;
foreach (var p in parameters)
cmd.Parameters.Add(p);
return cmd;
}
void RunSql(string cmdText, params SqlParameter[] parameters)
{
var cmd = CreateCommand(cmdText, parameters);
cmd.ExecuteNonQuery();
}
object RunSqlScalar(string cmdText, params SqlParameter[] parameters)
{
var cmd = CreateCommand(cmdText, parameters);
return cmd.ExecuteScalar();
}
}
public static class ReflectionUtil
{
public static bool InheritsOrImplements(this Type child, Type parent)
{
parent = ResolveGenericTypeDefinition(parent);
var currentChild = child.IsGenericType
? child.GetGenericTypeDefinition()
: child;
while (currentChild != typeof(object))
{
if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
return true;
currentChild = currentChild.BaseType != null
&& currentChild.BaseType.IsGenericType
? currentChild.BaseType.GetGenericTypeDefinition()
: currentChild.BaseType;
if (currentChild == null)
return false;
}
return false;
}
private static bool HasAnyInterfaces(Type parent, Type child)
{
return child.GetInterfaces()
.Any(childInterface =>
{
var currentInterface = childInterface.IsGenericType
? childInterface.GetGenericTypeDefinition()
: childInterface;
return currentInterface == parent;
});
}
private static Type ResolveGenericTypeDefinition(Type parent)
{
var shouldUseGenericType = true;
if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
shouldUseGenericType = false;
if (parent.IsGenericType && shouldUseGenericType)
parent = parent.GetGenericTypeDefinition();
return parent;
}
}
public static class ContextExtensions
{
public static string GetTableName(this DbContext context, Type tableType)
{
MethodInfo method = typeof(ContextExtensions).GetMethod("GetTableName", new Type[] { typeof(DbContext) })
.MakeGenericMethod(new Type[] { tableType });
return (string)method.Invoke(context, new object[] { context });
}
public static string GetTableName<T>(this DbContext context) where T : class
{
ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;
return objectContext.GetTableName<T>();
}
public static string GetTableName<T>(this ObjectContext context) where T : class
{
string sql = context.CreateObjectSet<T>().ToTraceString();
Regex regex = new Regex("FROM (?<table>.*) AS");
Match match = regex.Match(sql);
string table = match.Groups["table"].Value;
return table;
}
}
这个类从Visual Studio生成的XML文档文件中获取注释标记：
public class XmlAnnotationReader
{
public string XmlPath { get; protected internal set; }
public XmlDocument Document { get; protected internal set; }
public XmlAnnotationReader()
{
var assembly = Assembly.GetExecutingAssembly();
string resourceName = String.Format("{0}.App_Data.{0}.XML", assembly.GetName().Name);
this.XmlPath = resourceName;
using (Stream stream = assembly.GetManifestResourceStream(resourceName))
{
using (StreamReader reader = new StreamReader(stream))
{
XmlDocument doc = new XmlDocument();
//string result = reader.ReadToEnd();
doc.Load(reader);
this.Document = doc;
}
}
}
public XmlAnnotationReader(string xmlPath)
{
this.XmlPath = xmlPath;
if (File.Exists(xmlPath))
{
XmlDocument doc = new XmlDocument();
doc.Load(this.XmlPath);
this.Document = doc;
}
else
throw new FileNotFoundException(String.Format("Could not find the XmlDocument at the specified path: {0}\r\nCurrent Path: {1}", xmlPath, Assembly.GetExecutingAssembly().Location));
}
/// <summary>
/// Retrievethe XML comments documentation for a given resource
/// Eg. ITN.Data.Models.Entity.TestObject.MethodName
/// </summary>
/// <returns></returns>
public string GetCommentsForResource(string resourcePath, XmlResourceType type)
{
XmlNode node = Document.SelectSingleNode(String.Format("//member[starts-with(@name, '{0}:{1}')]/summary", GetObjectTypeChar(type), resourcePath));
if (node != null)
{
string xmlResult = node.InnerText;
string trimmedResult = Regex.Replace(xmlResult, @"\s+", " ");
return trimmedResult;
}
return string.Empty;
}
/// <summary>
/// Retrievethe XML comments documentation for a given resource
/// Eg. ITN.Data.Models.Entity.TestObject.MethodName
/// </summary>
/// <returns></returns>
public ObjectDocumentation[] GetCommentsForResource(Type objectType)
{
List<ObjectDocumentation> comments = new List<ObjectDocumentation>();
string resourcePath = objectType.FullName;
PropertyInfo[] properties = objectType.GetProperties();
FieldInfo[] fields = objectType.GetFields();
List<ObjectDocumentation> objectNames = new List<ObjectDocumentation>();
objectNames.AddRange(properties.Select(x => new ObjectDocumentation() { PropertyName = x.Name, Type = XmlResourceType.Property }).ToList());
objectNames.AddRange(properties.Select(x => new ObjectDocumentation() { PropertyName = x.Name, Type = XmlResourceType.Field }).ToList());
foreach (var property in objectNames)
{
XmlNode node = Document.SelectSingleNode(String.Format("//member[starts-with(@name, '{0}:{1}.{2}')]/summary", GetObjectTypeChar(property.Type), resourcePath, property.PropertyName ));
if (node != null)
{
string xmlResult = node.InnerText;
string trimmedResult = Regex.Replace(xmlResult, @"\s+", " ");
property.Documentation = trimmedResult;
comments.Add(property);
}
}
return comments.ToArray();
}
/// <summary>
/// Retrievethe XML comments documentation for a given resource
/// </summary>
/// <param name="objectType">The type of class to retrieve documenation on</param>
/// <param name="propertyName">The name of the property in the specified class</param>
/// <param name="resourceType"></param>
/// <returns></returns>
public string GetCommentsForResource(Type objectType, string propertyName, XmlResourceType resourceType)
{
List<ObjectDocumentation> comments = new List<ObjectDocumentation>();
string resourcePath = objectType.FullName;
string scopedElement = resourcePath;
if (propertyName != null && resourceType != XmlResourceType.Type)
scopedElement += "." + propertyName;
XmlNode node = Document.SelectSingleNode(String.Format("//member[starts-with(@name, '{0}:{1}')]/summary", GetObjectTypeChar(resourceType), scopedElement));
if (node != null)
{
string xmlResult = node.InnerText;
string trimmedResult = Regex.Replace(xmlResult, @"\s+", " ");
return trimmedResult;
}
return string.Empty;
}
private string GetObjectTypeChar(XmlResourceType type)
{
switch (type)
{
case XmlResourceType.Field:
return "F";
case XmlResourceType.Method:
return "M";
case XmlResourceType.Property:
return "P";
case XmlResourceType.Type:
return "T";
}
return string.Empty;
}
}
public class ObjectDocumentation
{
public string PropertyName { get; set; }
public string Documentation { get; set; }
public XmlResourceType Type { get; set; }
}
public enum XmlResourceType
{
Method,
Property,
Field,
Type
}
[Display(Name="Description here")]
您将使用：
[Description("Description here")]
public class DbDescriptionUpdater<TContext>
where TContext : System.Data.Entity.DbContext
{
public DbDescriptionUpdater(TContext context)
{
this.context = context;
}
Type contextType;
TContext context;
DbTransaction transaction;
public void UpdateDatabaseDescriptions()
{
contextType = typeof(TContext);
this.context = context;
var props = contextType.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
transaction = null;
try
{
context.Database.Connection.Open();
transaction = context.Database.Connection.BeginTransaction();
foreach (var prop in props)
{
if (prop.PropertyType.InheritsOrImplements((typeof(DbSet<>))))
{
var tableType = prop.PropertyType.GetGenericArguments()[0];
SetTableDescriptions(tableType);
}
}
transaction.Commit();
}
catch
{
if (transaction != null)
transaction.Rollback();
throw;
}
finally
{
if (context.Database.Connection.State == System.Data.ConnectionState.Open)
context.Database.Connection.Close();
}
}
private void SetTableDescriptions(Type tableType)
{
string fullTableName = context.GetTableName(tableType);
Regex regex = new Regex(@"(\[\w+\]\.)?\[(?<table>.*)\]");
Match match = regex.Match(fullTableName);
string tableName;
if (match.Success)
tableName = match.Groups["table"].Value;
else
tableName = fullTableName;
var tableAttrs = tableType.GetCustomAttributes(typeof(TableAttribute), false);
if (tableAttrs.Length > 0)
tableName = ((TableAttribute)tableAttrs[0]).Name;
var table_attrs = tableType.GetCustomAttributes(typeof(DescriptionAttribute), false);
if (table_attrs != null && table_attrs.Length > 0)
SetTableDescription(tableName, ((DescriptionAttribute)table_attrs[0]).Description);
foreach (var prop in tableType.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
{
if (prop.PropertyType.IsClass && prop.PropertyType != typeof(string))
continue;
var attrs = prop.GetCustomAttributes(typeof(DescriptionAttribute), false);
if (attrs != null && attrs.Length > 0)
SetColumnDescription(tableName, prop.Name, ((DescriptionAttribute)attrs[0]).Description);
}
}
private void SetColumnDescription(string tableName, string columnName, string description)
{
string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "','column',null) where objname = N'" + columnName + "';";
var prevDesc = RunSqlScalar(strGetDesc);
if (prevDesc == null)
{
RunSql(@"EXEC sp_addextendedproperty
@name = N'MS_Description', @value = @desc,
@level0type = N'Schema', @level0name = 'dbo',
@level1type = N'Table', @level1name = @table,
@level2type = N'Column', @level2name = @column;",
new SqlParameter("@table", tableName),
new SqlParameter("@column", columnName),
new SqlParameter("@desc", description));
}
else
{
RunSql(@"EXEC sp_updateextendedproperty
@name = N'MS_Description', @value = @desc,
@level0type = N'Schema', @level0name = 'dbo',
@level1type = N'Table', @level1name = @table,
@level2type = N'Column', @level2name = @column;",
new SqlParameter("@table", tableName),
new SqlParameter("@column", columnName),
new SqlParameter("@desc", description));
}
}
private void SetTableDescription(string tableName, string description)
{
string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "',null,null);";
var prevDesc = RunSqlScalar(strGetDesc);
if (prevDesc == null)
{
RunSql(@"EXEC sp_addextendedproperty
@name = N'MS_Description', @value = @desc,
@level0type = N'Schema', @level0name = 'dbo',
@level1type = N'Table', @level1name = @table;",
new SqlParameter("@table", tableName),
new SqlParameter("@desc", description));
}
else
{
RunSql(@"EXEC sp_updateextendedproperty
@name = N'MS_Description', @value = @desc,
@level0type = N'Schema', @level0name = 'dbo',
@level1type = N'Table', @level1name = @table;",
new SqlParameter("@table", tableName),
new SqlParameter("@desc", description));
}
}
DbCommand CreateCommand(string cmdText, params SqlParameter[] parameters)
{
var cmd = context.Database.Connection.CreateCommand();
cmd.CommandText = cmdText;
cmd.Transaction = transaction;
foreach (var p in parameters)
cmd.Parameters.Add(p);
return cmd;
}
void RunSql(string cmdText, params SqlParameter[] parameters)
{
var cmd = CreateCommand(cmdText, parameters);
cmd.ExecuteNonQuery();
}
object RunSqlScalar(string cmdText, params SqlParameter[] parameters)
{
var cmd = CreateCommand(cmdText, parameters);
return cmd.ExecuteScalar();
}
}
public static class ReflectionUtil
{
public static bool InheritsOrImplements(this Type child, Type parent)
{
parent = ResolveGenericTypeDefinition(parent);
var currentChild = child.IsGenericType
? child.GetGenericTypeDefinition()
: child;
while (currentChild != typeof(object))
{
if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
return true;
currentChild = currentChild.BaseType != null
&& currentChild.BaseType.IsGenericType
? currentChild.BaseType.GetGenericTypeDefinition()
: currentChild.BaseType;
if (currentChild == null)
return false;
}
return false;
}
private static bool HasAnyInterfaces(Type parent, Type child)
{
return child.GetInterfaces()
.Any(childInterface =>
{
var currentInterface = childInterface.IsGenericType
? childInterface.GetGenericTypeDefinition()
: childInterface;
return currentInterface == parent;
});
}
private static Type ResolveGenericTypeDefinition(Type parent)
{
var shouldUseGenericType = true;
if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
shouldUseGenericType = false;
if (parent.IsGenericType && shouldUseGenericType)
parent = parent.GetGenericTypeDefinition();
return parent;
}
}
public static class ContextExtensions
{
public static string GetTableName(this DbContext context, Type tableType)
{
MethodInfo method = typeof(ContextExtensions).GetMethod("GetTableName", new Type[] { typeof(DbContext) })
.MakeGenericMethod(new Type[] { tableType });
return (string)method.Invoke(context, new object[] { context });
}
public static string GetTableName<T>(this DbContext context) where T : class
{
ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;
return objectContext.GetTableName<T>();
}
public static string GetTableName<T>(this ObjectContext context) where T : class
{
string sql = context.CreateObjectSet<T>().ToTraceString();
Regex regex = new Regex("FROM (?<table>.*) AS");
Match match = regex.Match(sql);
string table = match.Groups["table"].Value;
return table;
}
}
您可以不使用ExceuteSqlCommand方法。在这里，您可以显式地定义要在表中添加的任何元属性。
http://msdn.microsoft.com/zh-cn/library/system.data.entity.database.executesqlcommand(v=vs.103).aspx
虽然这个问题是关于EF4的，但这个答案针对的是EF6，在问题被问出来后经过了一段时间，所以应该是适当的。
我认为注释应该放在迁移的 Up 和 Down 方法中，而不是某个 Seed 方法中。
所以，如@MichaelBrown所建议的那样，首先启用XML文档输出，并将文档文件作为嵌入式资源包含在您的项目中。
然后，通过使用一个 Convention 将注释转换为表/列注释。有一些调整需要进行，例如多行注释和消除过多的空格。
public class CommentConvention : Convention
{
public const string NewLinePlaceholder = "<<NEWLINE>>";
public CommentConvention()
{
var docuXml = new XmlDocument();
// Read the documentation xml
using (var commentStream = Assembly.GetExecutingAssembly().GetManifestResourceStream("Namespace.Documentation.xml"))
{
docuXml.Load(commentStream);
}
// configure class/table comment
Types()
.Having(pi => docuXml.SelectSingleNode($"//member[starts-with(@name, 'T:{pi?.FullName}')]/summary"))
.Configure((c, a) =>
{
c.HasTableAnnotation("Comment", GetCommentTextWithNewlineReplacement(a));
});
// configure property/column comments
Properties()
.Having(pi =>
docuXml.SelectSingleNode(
$"//member[starts-with(@name, 'P:{pi?.DeclaringType?.FullName}.{pi?.Name}')]/summary"))
.Configure((c, a) => { c.HasColumnAnnotation("Comment", GetCommentTextWithNewlineReplacement(a)); });
}
// adjust the documentation text to handle newline and whitespace
private static string GetCommentTextWithNewlineReplacement(XmlNode a)
{
if (string.IsNullOrWhiteSpace(a.InnerText))
{
return null;
}
return string.Join(
NewLinePlaceholder,
a.InnerText.Trim()
.Split(new string[] {"\r\n", "\r", "\n"}, StringSplitOptions.None)
.Select(line => line.Trim()));
}
}
在OnModelCreating方法中注册约定。
期望结果： 当创建新的迁移时，注释将作为注解包含，例如：
CreateTable(
"schema.Table",
c => new
{
Id = c.Decimal(nullable: false, precision: 10, scale: 0, identity: true,
annotations: new Dictionary<string, AnnotationValues>
{
{
"Comment",
new AnnotationValues(oldValue: null, newValue: "Commenting the Id Column")
},
}),
// ...
class CustomOracleSqlCodeGen : MigrationSqlGenerator
{
// the actual SQL generator
private readonly MigrationSqlGenerator _innerSqlGenerator;
public CustomOracleSqlCodeGen(MigrationSqlGenerator innerSqlGenerator)
{
_innerSqlGenerator = innerSqlGenerator;
}
public override IEnumerable<MigrationStatement> Generate(IEnumerable<MigrationOperation> migrationOperations, string providerManifestToken)
{
var ms = _innerSqlGenerator.Generate(AddCommentSqlStatements(migrationOperations), providerManifestToken);
return ms;
}
// generate additional SQL operations to produce comments
IEnumerable<MigrationOperation> AddCommentSqlStatements(IEnumerable<MigrationOperation> migrationOperations)
{
foreach (var migrationOperation in migrationOperations)
{
// the original inputted operation
yield return migrationOperation;
// create additional operations to produce comments
if (migrationOperation is CreateTableOperation cto)
{
foreach (var ctoAnnotation in cto.Annotations.Where(x => x.Key == "Comment"))
{
if (ctoAnnotation.Value is string annotation)
{
var commentString = annotation.Replace(
CommentConvention.NewLinePlaceholder,
Environment.NewLine);
yield return new SqlOperation($"COMMENT ON TABLE {cto.Name} IS '{commentString}'");
}
}
foreach (var columnModel in cto.Columns)
{
foreach (var columnModelAnnotation in columnModel.Annotations.Where(x => x.Key == "Comment"))
{
if (columnModelAnnotation.Value is AnnotationValues annotation)
{
var commentString = (annotation.NewValue as string)?.Replace(
CommentConvention.NewLinePlaceholder,
Environment.NewLine);
yield return new SqlOperation(
$"COMMENT ON COLUMN {cto.Name}.{columnModel.Name} IS '{commentString}'");
}
}
}
}
}
}
}
DbMigrationsConfiguration构造函数中，注册新的代码生成器（这是针对Oracle特定的，但对于其他SQL提供商也类似）。internal sealed class Configuration : DbMigrationsConfiguration<EntityFramework.Dev.ZdbTestContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = false;
var cg = GetSqlGenerator("Oracle.ManagedDataAccess.Client");
SetSqlGenerator("Oracle.ManagedDataAccess.Client", new CustomOracleSqlCodeGen(cg));
}
// ...
预期结果：从Up和Down方法的注释标注被翻译为SQL语句，以更改数据库中的注释。
现在已经到了2023年，我对Mahmood Dehghan提供的解决方案进行了更新，使用了.Net 6和Entity Framework Core 6 （这里），并对其进行了一些小修改，以便包含来自基类的属性（如果主类中不存在该属性），同时还向表中添加了扩展属性。