T4模板根据数据库表和列的Description生成代码的summary的终极解决方案

相信很多人都用T4模版生成代码，用T4模版生成标准代码真的很方便。我们经常根据表生成相关的代码，但是估计很多人都遇见过同一个问题，特别是我们在生成model的时候，代码中model中的Summary一直无法生成。这个问题也困扰了我很久，也找了很多方案，一直没有更好的方法。问题如下：

解决方案

为了生成summary需要额外的增加一个类，并在T4模版中引用这个类即可。这个类的作用是根据表名和列名提取数据表中列的description。

1. 首先查询数据库中所有表和列的基本信息

为了方便起见，我在数据库中创建了一个视图，视图结构如下：

sql 脚本如下：

SELECT   TOP (100) PERCENT COALESCE (T.name, OBJECT_NAME(C.object_id)) AS TableName, TB.TableDESC,
                C.name AS ColumnName, TYPE_NAME(C.user_type_id) AS DataType, D.definition AS DefaultSetting,
                C.is_nullable AS IsNullable, C.max_length AS MaxLength, COLUMNPROPERTY(C.object_id, C.name, 'PRECISION')
                AS Precision, P.value AS ColumnDESC
FROM      sys.columns AS C LEFT OUTER JOIN
                sys.table_types AS T ON T.type_table_object_id = C.object_id LEFT OUTER JOIN
                sys.default_constraints AS D ON C.object_id = D.parent_object_id AND
                D.parent_column_id = C.column_id LEFT OUTER JOIN
                sys.extended_properties AS P ON (P.major_id = C.object_id OR
                P.major_id = T.user_type_id) AND P.minor_id = C.column_id AND P.name = 'MS_Description' LEFT OUTER JOIN
                    (SELECT   INFORMATION_SCHEMA.TABLES.TABLE_NAME AS TableName, P.value AS TableDESC
                     FROM      INFORMATION_SCHEMA.TABLES LEFT OUTER JOIN
                                     sys.extended_properties AS P ON
                                     OBJECT_ID(INFORMATION_SCHEMA.TABLES.TABLE_SCHEMA + '.' + INFORMATION_SCHEMA.TABLES.TABLE_NAME)
                                      = P.major_id AND P.minor_id = 0
                     WHERE   (INFORMATION_SCHEMA.TABLES.TABLE_TYPE = 'BASE TABLE')) AS TB ON COALESCE (T.name,
                OBJECT_NAME(C.object_id)) = TB.TableName
WHERE   (COALESCE (SCHEMA_NAME(T.schema_id), OBJECT_SCHEMA_NAME(C.object_id)) = 'dbo')
ORDER BY TableName