我先使用Entity Framework 4.3.1代码进行显式迁移。如何在实体配置类或迁移中为列添加说明，以使其最终成为SQL Server(例如2008 R2)中列的说明？
我知道我可以为DbMigration类编写一个扩展方法，该方法将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方法中创建表后调用该扩展名。但是，有没有一种我尚未发现的优雅内在方式？拥有一个属性，迁移的变更检测逻辑可以支持并在支架式迁移中生成适当的方法调用，将是很好的。
最佳答案
我也需要这个所以我花了一天的时间在这里:
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
在您的
Migrations/Configuration.cs文件中，将此添加到Seed方法的末尾:DbDescriptionUpdater<ContextClass> updater = new DbDescriptionUpdater<ContextClass>(context);
updater.UpdateDatabaseDescriptions();
然后在Package Manager Console中键入
update-database，然后按Enter。而已。
该代码在实体类属性上使用
[Display(Name="Description here")]属性来设置描述。请报告任何错误或提出改进建议。
感谢
我已经从其他人那里使用过这些代码，我想说谢谢:
adding a column description
Check if a class is derived from a generic class
Get Database Table Name from Entity Framework MetaData
Generics in C#, using type of a variable as parameter