完美解决CodeSmith无法获取MySQL表及列Description说明注释的方案

问题描述：

　　CodeSmith是现在比较实用的代码生成器，但是我们发现一个问题：

　　使用CodeSmith编写MySQL模板的时候，会发现一个问题：MySQL数据表中的列说明获取不到，也就是column.Description。如图：

我们打开CodeSmith编写一个简单的Model实体类的示例模板如下：

<%-- 
Name:           MySQL Model实体模板
Author:         孤影[QQ:778078163]
Description:    CodeSmith连接MySQL生成Model实体模板
--%>

<%@ Template Language="C#" TargetLanguage="C#" ResponseEncoding="UTF-8" %>

<%@ Assembly Name="SchemaExplorer" %>
<%@ Import Namespace="SchemaExplorer" %>

<%@ Property Name="SourceTable" Type="SchemaExplorer.TableSchema" Description="目标数据表" %>
<%@ Property Name="ModelNamespace" Type="System.String" Description="Model实体所在的命名空间" %>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace <%=ModelNamespace %>
{
    /// <summary>
    /// <%=SourceTable.Description %>
    /// </summary>
    public class <%=SourceTable.Name %>
    {
        <%
            // 循环遍历 获取当前数据表中的所有列
            foreach(ColumnSchema column in SourceTable.Columns){
                Response.WriteLine(string.Format("// {0}",column.Description));
                Response.WriteLine(string.Format("public {0} {1} ;",GetCSharpVariableType(column),column.Name));
            }
        %>
    }
}

<script runat="template">
// 获取指定列对应的C#数据类型
public string GetCSharpVariableType(ColumnSchema column)
{
    if (column.Name.EndsWith("TypeCode")) return column.Name;
    
    switch (column.DataType)
    {
        case DbType.AnsiString: return "string";
        case DbType.AnsiStringFixedLength: return "string";
        case DbType.Binary: return "byte[]";
        case DbType.Boolean: return "bool";
        case DbType.Byte: return "byte";
        case DbType.Currency: return "decimal";
        case DbType.Date: return "DateTime";
        case DbType.DateTime: return "DateTime";
        case DbType.Decimal: return "decimal";
        case DbType.Double: return "double";
        case DbType.Guid: return "Guid";
        case DbType.Int16: return "short";
        case DbType.Int32: return "int";
        case DbType.Int64: return "long";
        case DbType.Object: return "object";
        case DbType.SByte: return "sbyte";
        case DbType.Single: return "float";
        case DbType.String: return "string";
        case DbType.StringFixedLength: return "string";
        case DbType.Time: return "TimeSpan";
        case DbType.UInt16: return "ushort";
        case DbType.UInt32: return "uint";
        case DbType.UInt64: return "ulong";
        case DbType.VarNumeric: return "decimal";
        default:
        {
            return "__UNKNOWN__" + column.NativeType;
        }
    }
}
</script>

然后我们点击生成，生成的代码如下图：

当然，使用SQL Server及其他数据库都是可以获取到的，这是为什么呢？

逼的没招没招了的时候，果断打开.NET Reflector，看看CodeSmith对SQL Server和MySQL二者，数据表生成操作的时候，有什么不同的地方，或者有什么缺少的地方。

CodeSmith中对MySQL操作的DLL组件位置是：“X:\...\CodeSmith\v7.0\SchemaProviders\SchemaExplorer.MySQLSchemaProvider.dll”

展开后，开始一个个找里面的方法，突然发现一个亮点：“GetTableColumns(string connectionString, TableSchema table);”

这个字面的意思不就是获取列数据么？打开看看。。。可惜，里面只是根据表查询所有列，并没有Description相关操作。

继续找，继续对比。。。最终终于找到问题了：

方法“GetExtendedProperties(string connectionString, SchemaObjectBase schemaObject);”里面的查询语句是：

string str = string.Format("SELECT EXTRA, COLUMN_DEFAULT, COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = '{0}' AND TABLE_NAME = '{1}' AND COLUMN_NAME = '{2}'", schema.Table.Database.Name, schema.Table.Name, schema.Name);

这个不就是获取Column列中的扩展属性的方法么？！

对比发现，SQL Server的dll里这个方法的下面，有返回Description，而MySQL正好没有！

二话不说，找到CodeSmith的源码包解压，翻出MySQL的项目：“X:\...\CodeSmith\v7.0\Samples\Samples\Projects\CSharp\MySQLSchemaProvider”

然后打开Visual Studio载入"MySQLSchemaProvider.csproj"，有很多错误，那是因为缺少了引用，添加CodeSmith\bin里面的相关引用即可。

需要引用的组件你可以在下面两个CodeSmith安装目录中找到：

“X:\...\CodeSmith\v7.0\bin\”、“X:\...\CodeSmith\v7.0\AddIns\”

添加引用之后，错误就全部没了：

然后我们果断开始修改代码、首先找到刚刚那个获取列扩展属性的方法：

“public ExtendedProperty[] GetExtendedProperties(string connectionString, SchemaObjectBase schemaObject)”

然后我们根据观察SQL Server的代码，发现MySQL里面这个方法：

在SQL语句查询的时候少查询了一项数据：“COLUMN_COMMENT”，于是我们首先修改它查询的SQL语句如下：

string commandText = string.Format(@"SELECT EXTRA, COLUMN_DEFAULT, COLUMN_TYPE, COLUMN_COMMENT
                                                      FROM INFORMATION_SCHEMA.COLUMNS
                                                      WHERE TABLE_SCHEMA = '{0}' AND TABLE_NAME = '{1}' AND COLUMN_NAME = '{2}'",
                                                      columnSchema.Table.Database.Name, columnSchema.Table.Name, columnSchema.Name);

既然上面查询了，按照正常的数据查询流程，下面应该遍历读取，然后返回吧？

于是继续看，下面有一个while，正是将上面查询出来的数据返回的，我们对比SQL Server的代码发现：

上面查询出来的每一项，下面都有获取返回，而我们刚刚添加的那个“COLUMN_COMMENT”则没有进行数据获取、没有怎么办？加呗~

获取每个数据后，最后统一将封装在“extendedProperties”中，于是我们也将获取到的Description添加进去，其与步骤省略。最终修改的代码如下：

public ExtendedProperty[] GetExtendedProperties(string connectionString, SchemaObjectBase schemaObject)
        {
            List<ExtendedProperty> extendedProperties = new List<ExtendedProperty>();

            if (schemaObject is ColumnSchema)
            {
                ColumnSchema columnSchema = schemaObject as ColumnSchema;

                string commandText = string.Format(@"SELECT EXTRA, COLUMN_DEFAULT, COLUMN_TYPE, COLUMN_COMMENT
                                                      FROM INFORMATION_SCHEMA.COLUMNS
                                                      WHERE TABLE_SCHEMA = '{0}' AND TABLE_NAME = '{1}' AND COLUMN_NAME = '{2}'",
                                                      columnSchema.Table.Database.Name, columnSchema.Table.Name, columnSchema.Name);

                using (DbConnection connection = CreateConnection(connectionString))
                {
                    connection.Open();

                    DbCommand command = connection.CreateCommand();
                    command.CommandText = commandText;
                    command.Connection = connection;

                    using (IDataReader reader = command.ExecuteReader(CommandBehavior.CloseConnection))
                    {
                        while (reader.Read())
                        {
                            string extra = reader.GetString(0).ToLower();
                            bool columndefaultisnull = reader.IsDBNull(1);
                            string columndefault = "";
                            if (!columndefaultisnull)
                            {
                                columndefault = reader.GetString(1).ToUpper();
                            }
                            string columntype = reader.GetString(2).ToUpper();
                            string columncomment = reader.GetString(3);

                            bool isIdentity = (extra.IndexOf("auto_increment") > -1);
                            extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.IsIdentity, isIdentity, columnSchema.DataType));

                            if (isIdentity)
                            {
                                /*
                                MySQL auto_increment doesn't work exactly like SQL Server's IDENTITY
                                I believe that auto_increment is equivalent to IDENTITY(1, 1)
                                However, auto_increment behaves differently from IDENTITY when used
                                with multi-column primary keys.  See the MySQL Reference Manual for details.
                                */
                                extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.IdentitySeed, 1, columnSchema.DataType));
                                extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.IdentityIncrement, 1, columnSchema.DataType));
                            }

                            extendedProperties.Add(new ExtendedProperty("CS_ColumnDefaultIsNull", columndefaultisnull, DbType.Boolean)); // Added for Backwards Compatibility.
                            extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.DefaultValue, columndefault, DbType.String));
                            extendedProperties.Add(new ExtendedProperty("CS_ColumnDefault", columndefault, DbType.String)); // Added for Backwards Compatibility.
                            extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.SystemType, columntype, DbType.String));
                            extendedProperties.Add(new ExtendedProperty("CS_ColumnType", columntype, DbType.String)); // Added for Backwards Compatibility.
                            extendedProperties.Add(new ExtendedProperty("CS_ColumnExtra", extra.ToUpper(), DbType.String));
                            extendedProperties.Add(new ExtendedProperty("CS_Description", columncomment, DbType.String));
                        }

                        if (!reader.IsClosed)
                            reader.Close();
                    }

                    if (connection.State != ConnectionState.Closed)
                        connection.Close();
                }
            }
            if (schemaObject is TableSchema)
            {
                TableSchema tableSchema = schemaObject as TableSchema;
                string commandText = string.Format(@"SHOW CREATE TABLE `{0}`.`{1}`", tableSchema.Database.Name, tableSchema.Name);

                using (DbConnection connection = CreateConnection(connectionString))
                {
                    connection.Open();

                    DbCommand command = connection.CreateCommand();
                    command.CommandText = commandText;
                    command.Connection = connection;

                    using (IDataReader reader = command.ExecuteReader(CommandBehavior.CloseConnection))
                    {
                        while (reader.Read())
                        {
                            string createtable = reader.GetString(1);
                            extendedProperties.Add(new ExtendedProperty("CS_CreateTableScript", createtable, DbType.String));
                        }

                        if (!reader.IsClosed)
                            reader.Close();
                    }

                    if (connection.State != ConnectionState.Closed)
                        connection.Close();
                }
            }

            return extendedProperties.ToArray();
        }

然后我们F6生成一个修改后的dll组件"SchemaExplorer.MySQLSchemaProvider.dll"。

找到默认的dll：“X:\...\CodeSmith\v7.0\SchemaProviders\SchemaExplorer.MySQLSchemaProvider.dll”，替.....不行，还是先备份一下。。。哈哈

然后替换。打开重启CodeSmith，再次生成。。。-_-#　我去！这是在逗我么。

再次回到Visual Studio中仔细看看整个方法，最后发现。。服了。它的这个方法的判断逻辑是：

public ExtendedProperty[] GetExtendedProperties(string connectionString, SchemaObjectBase schemaObject)

{

　　List<要返回的东西>......

　　if(schemaObject 是一个 ColumnSchema)// 如果是一个列对象

　　{

　　　　// 这里面也就是我们刚刚改的，获取列说明部分的代码

　　}

　　if(schemaObject 是一个 TableSchema)// 完全没有注意下面的这个判断，如果是一个表对象！！！

　　{

　　　　// 这里也就是我们下面要动手脚的地方了。

　　}

}

废话不多说。直接上这个方法最终的代码：

        public ExtendedProperty[] GetExtendedProperties(string connectionString, SchemaObjectBase schemaObject)
        {
            List<ExtendedProperty> extendedProperties = new List<ExtendedProperty>();

            if (schemaObject is ColumnSchema)
            {
                ColumnSchema columnSchema = schemaObject as ColumnSchema;

                string commandText = string.Format(@"SELECT EXTRA, COLUMN_DEFAULT, COLUMN_TYPE, COLUMN_COMMENT
                                                      FROM INFORMATION_SCHEMA.COLUMNS
                                                      WHERE TABLE_SCHEMA = '{0}' AND TABLE_NAME = '{1}' AND COLUMN_NAME = '{2}'",
                                                      columnSchema.Table.Database.Name, columnSchema.Table.Name, columnSchema.Name);

                using (DbConnection connection = CreateConnection(connectionString))
                {
                    connection.Open();

                    DbCommand command = connection.CreateCommand();
                    command.CommandText = commandText;
                    command.Connection = connection;

                    using (IDataReader reader = command.ExecuteReader(CommandBehavior.CloseConnection))
                    {
                        while (reader.Read())
                        {
                            string extra = reader.GetString(0).ToLower();
                            bool columndefaultisnull = reader.IsDBNull(1);
                            string columndefault = "";
                            if (!columndefaultisnull)
                            {
                                columndefault = reader.GetString(1).ToUpper();
                            }
                            string columntype = reader.GetString(2).ToUpper();
                            string columncomment = reader.GetString(3);

                            bool isIdentity = (extra.IndexOf("auto_increment") > -1);
                            extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.IsIdentity, isIdentity, columnSchema.DataType));

                            if (isIdentity)
                            {
                                /*
                                MySQL auto_increment doesn't work exactly like SQL Server's IDENTITY
                                I believe that auto_increment is equivalent to IDENTITY(1, 1)
                                However, auto_increment behaves differently from IDENTITY when used
                                with multi-column primary keys.  See the MySQL Reference Manual for details.
                                */
                                extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.IdentitySeed, 1, columnSchema.DataType));
                                extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.IdentityIncrement, 1, columnSchema.DataType));
                            }

                            extendedProperties.Add(new ExtendedProperty("CS_ColumnDefaultIsNull", columndefaultisnull, DbType.Boolean)); // Added for Backwards Compatibility.
                            extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.DefaultValue, columndefault, DbType.String));
                            extendedProperties.Add(new ExtendedProperty("CS_ColumnDefault", columndefault, DbType.String)); // Added for Backwards Compatibility.
                            extendedProperties.Add(new ExtendedProperty(ExtendedPropertyNames.SystemType, columntype, DbType.String));
                            extendedProperties.Add(new ExtendedProperty("CS_ColumnType", columntype, DbType.String)); // Added for Backwards Compatibility.
                            extendedProperties.Add(new ExtendedProperty("CS_ColumnExtra", extra.ToUpper(), DbType.String));
                            extendedProperties.Add(new ExtendedProperty("CS_Description", columncomment, DbType.String));
                        }

                        if (!reader.IsClosed)
                            reader.Close();
                    }

                    if (connection.State != ConnectionState.Closed)
                        connection.Close();
                }
            }
            if (schemaObject is TableSchema)
            {
                TableSchema tableSchema = schemaObject as TableSchema;
                string commandText = string.Format(@"SHOW CREATE TABLE `{0}`.`{1}`", tableSchema.Database.Name, tableSchema.Name);

                using (DbConnection connection = CreateConnection(connectionString))
                {
                    connection.Open();

                    DbCommand command = connection.CreateCommand();
                    command.CommandText = commandText;
                    command.Connection = connection;

                    using (IDataReader reader = command.ExecuteReader(CommandBehavior.CloseConnection))
                    {
                        while (reader.Read())
                        {
                            string createtable = reader.GetString(1);
                            extendedProperties.Add(new ExtendedProperty("TS_Description", createtable, DbType.String));
                            int engineIndex = createtable.LastIndexOf("ENGINE");
                            int commentIndex = createtable.LastIndexOf("COMMENT=");
                            string tableDescription = reader.GetString(0);
                            if (commentIndex > engineIndex)
                            {
                                tableDescription = createtable.Substring(commentIndex + 9).Replace("'", "");
                            }
                            extendedProperties.Add(new ExtendedProperty("CS_Description", tableDescription, DbType.String));

                        }

                        if (!reader.IsClosed)
                            reader.Close();
                    }

                    if (connection.State != ConnectionState.Closed)
                        connection.Close();
                }
            }

            return extendedProperties.ToArray();
        }

重新生成，替换。。。重启CodeSmith，链接MySQL生成。。。。必然果断Ok：

网上当然也有很多例子，不过都是只处理了列的说明，没有处理表的说明。

我这个处理表说明是通过截取已获得的CreateTableScript里面的数据，获取的表说明。

码字不容易，感觉不错的话，请不要忘了点赞哦~(*^_^ *)

【本章来自 孤影'Blog：http://www.cnblogs.com/LonelyShadow，码字不容易，转载请注明出处。】