将DataTable序列化为Json格式

很多时候我们希望将查询出的数据源格式（如：List<T>、DataTable等）转换为Json格式，便于前台的JS的处理，尤其是在使用Extjs框架的时候，JsonStore异步（Ajax）请求的数据格式就是Json，那么后台序列化的就显得非常重要！
当然序列化很简单，因为微软已经提供了序列化的方法，在引用命名空间（using System.Web.Script.Serialization;）后，即可使用内置的JavaScriptSerializer. Serialize()方法，使用方式如下：
JavaScriptSerializer jss = new JavaScriptSerializer();
string strJson = jss.Serialize(t); //T t为泛型
一般类型都能顺利序列化,但是如果此时传入的类型T为DataTable,那么就会发生异常了,出现”序列化类型为“System.Reflection.Module”的对象时检测到循环引用。”的错误提示.

究其原因,猜测可能是DataTable的成员DataRow的Table属性又引用了DataTable本身，真正原因我没去分析。下面提供一种解决方式：
/*
* Copyright: Copyright: ?2010 Twilight软件开发工作室
* Author: xuzhihong
* Create date: 2010-3-24
* Description: 将DataTable转换JSON对象
*
*/

public class ConventDataTableToJson
{
/// <summary>
/// 序列化方法（带分页）
/// </summary>
/// <param name="dt"></param>
/// <returns></returns>
public static string Serialize(DataTable dt)
{
List<Dictionary<string, object>> list = new List<Dictionary<string, object>>();
foreach (DataRow dr in dt.Rows)
{
Dictionary<string, object> result = new Dictionary<string, object>();
foreach (DataColumn dc in dt.Columns)
{
result.Add(dc.ColumnName, dr[dc].ToString());
}
list.Add(result);
}
int count = 0;
try
{
count = Convert.ToInt32(dt.TableName);
}
catch (System.Exception ex)
{
count = dt.Rows.Count;
}
string strReturn = "";
if (count == 0)
{
strReturn = "{/"totalCount/":0,/"data/":[]}";
}
else
{
strReturn = ConventToJson(list, count);
}
return strReturn;
}

/// <summary>
/// 转换为JSON对象
/// </summary>
/// <returns></returns>
public static string ConventToJson<T>(List<T> list, int count)
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
string strJson = serializer.Serialize(list);
strJson = strJson.Substring(1);
strJson = strJson.Insert(0, "{totalCount:" + count + ",data:[");
strJson += "}";

return strJson;
}

/// <summary>
/// 不需要分页
/// </summary>
/// <param name="dt"></param>
/// <param name="flag">false</param>
/// <returns></returns>
public static string Serialize(DataTable dt,bool flag)
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
List<Dictionary<string, object>> list = new List<Dictionary<string, object>>();
foreach (DataRow dr in dt.Rows)
{
Dictionary<string, object> result = new Dictionary<string, object>();
foreach (DataColumn dc in dt.Columns)
{
result.Add(dc.ColumnName, dr[dc].ToString());
}
list.Add(result);
}
return serializer.Serialize(list); ;
}
}

原理非常简单，主要思想就是利用Dictionary<string, object>字典，将DataRow属性名/值存储在List<Dictionary<string, object>>中，这样List<T>是能被正常序列化的。

说明：在带分页的序列化方法，我做了一个格式设置，主要是为了序列化为Extjs的JsonStore要求的格式，序列化的Json字符串如下：（下面的字符串只有一条记录）
{totalCount:1,data:[{"FID":"71e78220-8074-4f17-9f7b-c2413bf0ac4e","FTaskID":"b4f42e8e-a457-424c-888c-b874128ffb57","FTaskCode":"20110119-01","FTestItemID":"9a8c3c7a-f8c2-41f0-a279-4d50575f5f89","FTestItemName":"盖总成分离指安装高度及分离指端面跳动量测定","FAssignTag":"0","FTestCompleteTag":"0","FType":"1","FReTestTag":"1","FReTestFromTag":"1","FHasOriginalFile":"0","FInSampleNumber":"","FSerialNumber":"","FTestRemark":"","FReceiver":"","FReceiveTime":"","FEndTag":"1","FSampleModel":"234","FIsUrgent":"0","FSampleName":"","RowNumber":"1"}]}

其中：totalCount和dat对应JS的totalProperty和root配置项。

var store = new Ext.data.JsonStore({
proxy: new Ext.data.HttpProxy({ url: Vars.Url}),
idProperty: 'FID',
root: 'data',
totalProperty: 'totalCount',
fields: ['FID', 'FCode', 'FDuName', 'FSampleName'],
baseParams: { sign: 'GetByCondition', start: 0, limit: Vars.PageSize, condition: Ext.encode(Vars.Condition) }
});