DataTable转换为Json字符串的三种方法

//第一种：使用StringBuilder 

 public string DataTableToJson(DataTable table)
     {
         var JsonString = new StringBuilder();
         if (table.Rows.Count > )
         {
             JsonString.Append("[");
             for (int i = ; i < table.Rows.Count; i++)
             {
                 JsonString.Append("{");
                 for (int j = ; j < table.Columns.Count; j++)
                 {
                     if (j < table.Columns.Count - )
                     {
                         JsonString.Append("\"" + table.Columns[j].ColumnName.ToString() + "\":" + "\"" + table.Rows[i][j].ToString() + "\",");
                     }
                     else if (j == table.Columns.Count - )
                     {
                         JsonString.Append("\"" + table.Columns[j].ColumnName.ToString() + "\":" + "\"" + table.Rows[i][j].ToString() + "\"");
                     }
                 }
                 if (i == table.Rows.Count - )
                 {
                     JsonString.Append("}");
                 }
                 else
                 {
                     JsonString.Append("},");
                 }
             }
             JsonString.Append("]");
         }
         return JsonString.ToString();
     }  

//第二种：使用JavaScriptSerializer序列化数据

 using System.Web.Script.Serialization;  

 public string DataTableToJsonWithJavaScriptSerializer(DataTable table)
    {
        JavaScriptSerializer jsSerializer = new JavaScriptSerializer();
        List < Dictionary < string, object >> parentRow = new List < Dictionary < string, object >> ();
        Dictionary < string, object > childRow;
        foreach(DataRow row in table.Rows)
        {
            childRow = new Dictionary < string, object > ();
            foreach(DataColumn col in table.Columns)
            {
                childRow.Add(col.ColumnName, row[col]);
            }
            parentRow.Add(childRow);
        }
        return jsSerializer.Serialize(parentRow);
    }    

//第三种：使用Json.Net DLL (Newtonsoft)。

这个方法中要添加Json.Net DLL引用，我们可以从Newtonsoft下载Json.Net DLL，再导入命名空间，代码如下：

 using Newtonsoft.Json;  

 public string DataTableToJsonWithJsonNet(DataTable table)
    {
     string JsonString=string.Empty;
     JsonString = JsonConvert.SerializeObject(table);
     return JsonString;
    }