通过DataTable 返回Json格式，用于绑定Easyui tree

/// <summary>
/// 根据DataTable生成Json树结构  調用GetTreeJsonByTable(datatable, "MENUID", "MENUNAME", "PARENTID", "0");
/// </summary>
/// <param name="tabel">数据源</param>
/// <param name="idCol">ID列</param>
/// <param name="txtCol">Text列</param>
/// <param name="rela">关系字段</param>
/// <param name="pId">父ID</param>
///<returns>easyui tree json格式</returns>
StringBuilder treeResult = new StringBuilder();
StringBuilder treesb = new StringBuilder();
public string GetTreeJsonByTable(DataTable tabel, string idCol, string txtCol, string rela, object pId)
{
string treeJson = string.Empty;

treeResult.Append(treesb.ToString());
treesb.Clear();
if (tabel.Rows.Count > 0)
{
treesb.Append("[");

string filer = string.Empty;
if (pId.ToString() == "")
{
filer = string.Format("{0} is null", rela);
}
else
{
filer = string.Format("{0}='{1}'", rela, pId);
}
DataRow[] rows = tabel.Select(filer);
if (rows.Length > 0)
{
foreach (DataRow row in rows)
{
treesb.Append("{\"id\":\"" + row[idCol]
+ "\",\"text\":\"" + row[txtCol]
+ "\",\"state\":\"open\"");

if (tabel.Select(string.Format("{0}='{1}'", rela, row[idCol])).Length > 0)
{
treesb.Append(",\"children\":");
GetTreeJsonByTable(tabel, idCol, txtCol, rela, row[idCol]);
treeResult.Append(treesb.ToString());
treesb.Clear();
}
treeResult.Append(treesb.ToString());
treesb.Clear();
treesb.Append("},");
}
treesb = treesb.Remove(treesb.Length - 1, 1);
}
treesb.Append("]");
treeResult.Append(treesb.ToString());
treeJson = treeResult.ToString();
treesb.Clear();
}

return treeJson;
}

调用方法：
MenuTreeHelper treeHelper = new MenuTreeHelper();
return treeHelper.GetTreeJsonByTable(datatable, "ID", "TEXT", "PARENTNO", "0");