不好意思，借首页作个广告，给大家介绍个开源的数据访问组件Data Access Component，项目网站:http://dac.codeplex.com .
项目描述:
数据访问组件，提供了一组类库和一个代码生成工具，使.net项目中数据访问更简化.
功能:
- 多种数据库支持.
- 提供DataSet, DataTable 和数据实体查询.
- 执行SQL脚本及存储过程.
- 条件表达式.
- 常用SQL方法, 如MAX, MIN等可能被应用在查询中.
- 数据实体代码及XML文件生成.
使用:
基本功能:
1. 使用 "EntitiesGenerator" 生成工具生成实体项目。
参见 blog： How to use the "Enties Generator" tool to create an entities project.
2. 添加一个文件名为"connection.config"的数据库连接配置文件，到应用程序的运行目录，文件格式及内容如下：
<?xml version="1.0" encoding="utf-8" ?>
<connections>
<connection databaseType="SQL">Data Source=.\SQLEXPRESS;AttachDbFilename="|DataDirectory|Database1.mdf";
Integrated Security=True;User Instance=True</connection>
</connections>
3. 假定我们有个实体类，名叫 "Issue", 可以使用以下代码将它插入数据库
RaisingStudio.Data.Providers.DataContext dc = new RaisingStudio.Data.Providers.DataContext();
dc.Insert<Issue>(issue);
4. 更新实体.
dc.Update<Issue>(issue);
5. 删除实体, 可以通过给定实体或实体的主键值进行。
dc.Delete<Issue>(issue);
dc.Delete<Issue>(issueID);
6. 查询实体, 通过三个不同的方法，可以分别获得 IEnumerable<T>, IList<T> or DataTable 作为返回结果。
IEnumerable<Issue> query = dc.Query<Issue>();
foreach(Issue issue in query)
{
}
IList<Issue> issueList = dc.QueryForList<Issue>();
DataTable dataTable = dc.QueryForDataTable<Issue>(Issue._.IssueID > 1);
7. 可以通过GetData()方法，查询单个实体，使用包含主键值的实体，主键值或条件表达式作为参数。
Issue issue = new Issue();
issue.IssueID = 2;
issue = dc.GetData<Issue>(issue);
Issue issue = dc.GetData<Issue>(2);
Issue issue = dc.GetData<Issue>(Issue._.IssueID == 2);
8. 更新DataTable.
int result = dc.UpdateDataTable<Issue>(dataTable);
高级特性:
1. 常用SQL方法, 包括 GetCount, GetMin, GetMax, GetSum and GetAvg.
int result = dc.GetCount<Issue>();
object minValue = dc.GetMin<Issue>(Issue._.Progress);
decimal maxValue = Convert.ToDecimal(dc.GetMax<Issue>(Issue._.Progress,
Issue._.Title == "test title"));
2. Save 和 Exists.
int result = dc.Save<Issue>(issue);
bool saved = dc.Exists<Issue>(issue);
bool ex = dc.Exists<Issue>(Issue._.Title == "test title");
3. 部分列.
Issue issue = dc.GetData<issue>(2, Issue._.Status);
issue.Status = IssueStatus.Fixed;
int result = dc.Update<Issue>(issue, Issue._.Status);
4. 批量操作.
int result = dc.Delete<issue>(Issue._.Status == IssueStatus.Fixed);
result = dc.Update<Issue>(issue, Issue._.Status == IssueStatus.Fixed, Issue._.Status);
5. 排序, 使用 "OrderBy" 方法或 ^ 和 ^ ! 运算符应用在查询中，可以对查询进行排序.
IEnumerable<Issue> query = dc.Query<Issue>(Issue.All.OrderBy(Issue._.IssueID));
query = dc.Query<Issue>(Issue._.Status == IssueStatus.Fixed ^ Issue._.IssueID);
6. 分页.
IList<Issue> issueList = dc.QueryForList<Issue>(Issue.All, 0, 100);
7. 事务.
try
{
this.dc.BeginTransaction();
try
{
int result = this.dc.Insert<Issue>(issue);
this.dc.CommitTransaction();
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex);
this.dc.RollbackTransaction();
throw;
}
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex);
throw;
}
8. 多主键.
MutipleKeysTable mt = dc.GetData<MutipleKeysTable>(new object[] { key1, key2 },
MutipleKeysTable.Except(MutipleKeysTable._.Value2));
9. 使用 common command 查询.
CommonCommand cmd = new CommonCommand();
cmd.CommandText = string.Format("SELECT [IssueID], [{0}] FROM .[Issue] WHERE [{0}] = @p1", Issue._.Title);
cmd.Parameters.Add("@p1", "test title");
Issue issue = dc.GetData<Issue>(cmd);
10. 执行 common command, 支持 ExecuteForDataTable, ExecuteForList, ExecuteQuery, ExecuteReader, ExecuteScalar 和 ExecuteNoQuery 等方法.
RaisingStudio.Data.CommonCommand cmd = new CommonCommand(
string.Format("UPDATE .[{0}] SET [{1}] = [{1}] + 1 WHERE [{2}] = @p1",
Issue._, Issue._.Progress, Issue._.IssueID));
cmd.AddParameter("@p1", System.Data.DbType.Int32, maxID);
int result = this.dc.ExecuteNoQuery<Issue>(cmd);
11. SQL 脚本日志.
DataContext dc = new DataContext();
dc.Log = System.Console.Out;
12. 多种数据库 providers, 添加如下的 xml 项到 "providers.config" 配置文件中, 就可以在 "connections.config" 中使用.
<provider
name="MYSQL"
description="MySQL, MySQL provider "
enabled="false"
assemblyName="MySql.Data, Version=5.2.5.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d"
connectionClass="MySql.Data.MySqlClient.MySqlConnection"
commandClass="MySql.Data.MySqlClient.MySqlCommand"
parameterClass="MySql.Data.MySqlClient.MySqlParameter"
parameterDbTypeClass="MySql.Data.MySqlClient.MySqlDbType"
parameterDbTypeProperty="MySqlDbType"
dataAdapterClass="MySql.Data.MySqlClient.MySqlDataAdapter"
commandBuilderClass="MySql.Data.MySqlClient.MySqlCommandBuilder"
usePositionalParameters="false"
useParameterPrefixInSql="true"
useParameterPrefixInParameter="true"
parameterPrefix="?"
allowMARS="false"
/>
13. 自定义数据类型“转换器”, 以下就是一个 "TypeConverter" 示例代码，及如何配置到 "converters.config" 配置文件中.
public class PointConverter : IDbTypeConverter
{
#region IDbTypeConvertermember
public object ConvertFromDbType(object value)
{
string s = value as string;
if (!string.IsNullOrEmpty(s))
{
string[] sa = s.Split(',');
if ((sa != null) && (sa.Length == 3))
{
int x = int.Parse(sa[0]);
int y = int.Parse(sa[1]);
int z = int.Parse(sa[2]);
return new Point(x, y, z);
}
}
return null;
}
public object ConvertToDbType(object value)
{
if (value is Point)
{
Point point = (Point)value;
return point.ToString();
}
return null;
}
#endregion
}
<converter type="RaisingStudio.Data.Entities.Point,
RaisingStudio.Data.Entities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"
dbType="string"
converterType="RaisingStudio.Data.Entities.PointConverter,
RaisingStudio.Data.Entities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
</converter>
14. “实体定义”配置, "*.definition.xml" 文件可以作为资源文件嵌入到程序集在，也可以留在文件系统上，"EntitiesGenerator" 实体生成工具生在项目是采用的嵌入资源的方式， 如果要使用文件的方式，则需要配置一个名叫"definitions.config"的配置文件，样式如下：
<?xml version="1.0" encoding="utf-8"?>
<definitionsConfig xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<aliases>
<alias name="UTIssue" type="UnitTest.UTIssue, UnitTest, Version=1.0.0.0,
Culture=neutral, PublicKeyToken=null" />
</aliases>
<definitions>
<definition name="UTIssue" resource="definitions/Issue.definition.xml" />
<definition name="UTSystemUser" resource="definitions/SystemUser.definition.xml" />
</definitions>
</definitionsConfig>
15. Common command 管理器. 把 SQL脚本配置在 "commands.config" 中后，可以用如下代码读取使用。
<?xml version="1.0" encoding="utf-8" ?>
<commands parameterPrefix=":">
<command name="select">SELECT * FROM DAC_ISSUE</command>
<command name="select2">
<![CDATA[
SELECT * FROM DAC_USER
]]>
</command>
<command name="select3" commandType="StoredProcedure">SELECT_DAC_ISSUE</command>
<command name="select4">
<![CDATA[
SELECT * FROM DAC_ISSUE DI
WHERE DI.ISSUE_ID = :ISSUE_ID
]]>
</command>
</commands>
CommonCommand cmd = CommandManager.Instance.GetCommand("select");
System.Data.DataTable dt = this.dc.ExecuteForDataTable(cmd);