private DataTable getData()
{
DataTable dt = new DataTable();
dt.Columns.Add("编号", typeof(Int32));
dt.Columns.Add("姓名", typeof(string));
dt.Columns.Add("性别", typeof(string));
dt.Columns.Add("学历", typeof(string));
dt.Rows.Add(1, "王超", "男", "本科");
dt.Rows.Add(2, "周丽", "女", "专科");
dt.Rows.Add(3, "李娟", "女", "专科");
dt.Rows.Add(4, "杨明", "男", "硕士");
dt.Rows.Add(5, "张德", "男", "本科");
return dt;
}

public string DataTableToJson(DataTable table)
{
var JsonString = new StringBuilder();
if (table.Rows.Count > 0)
{
JsonString.Append("[");
for (int i = 0; i < table.Rows.Count; i++)
{
JsonString.Append("{");
for (int j = 0; j < table.Columns.Count; j++)
{
if (j < table.Columns.Count - 1)
{
JsonString.Append("\"" + table.Columns[j].ColumnName.ToString() + "\":" + "\"" + table.Rows[i][j].ToString() + "\",");
}
else if (j == table.Columns.Count - 1)
{
JsonString.Append("\"" + table.Columns[j].ColumnName.ToString() + "\":" + "\"" + table.Rows[i][j].ToString() + "\"");
}
}
if (i == table.Rows.Count - 1)
{
JsonString.Append("}");
}
else
{
JsonString.Append("},");
}
}
JsonString.Append("]");
}
return JsonString.ToString(); 
}

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); 
}

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

using System;
using Susing System.Data;
public partial class Default2 : System.Web.UI.Page
private string sasss;

protected void Page_Load(object sender, EventArgs e)
{
DataTable table = getData();
sasss = DataTableToJson(table);

Response.Write(sasss + "<br/>");

}
public string DataTableToJson(DataTable table)
{
var JsonString = new StringBuilder();
if (table.Rows.Count > 0)
{
JsonString.Append("[");
for (int i = 0; i < table.Rows.Count; i++)
{
JsonString.Append("{");
for (int j = 0; j < table.Columns.Count; j++)
{
if (j < table.Columns.Count - 1)
{
JsonString.Append("\"" + table.Columns[j].ColumnName.ToString() + "\":" + "\"" + table.Rows[i][j].ToString() + "\",");
}
else if (j == table.Columns.Count - 1)
{
JsonString.Append("\"" + table.Columns[j].ColumnName.ToString() + "\":" + "\"" + table.Rows[i][j].ToString() + "\"");
}
}
if (i == table.Rows.Count - 1)
{
JsonString.Append("}");
}
else
{
JsonString.Append("},");
}
}
JsonString.Append("]");
}
return JsonString.ToString(); 
}

private DataTable getData()
{
DataTable dt = new DataTable();
dt.Columns.Add("编号", typeof(Int32));
dt.Columns.Add("姓名", typeof(string));
dt.Columns.Add("性别", typeof(string));
dt.Columns.Add("学历", typeof(string));
dt.Rows.Add(1, "王超", "男", "本科");
dt.Rows.Add(2, "周丽", "女", "专科");
dt.Rows.Add(3, "李娟", "女", "专科");
dt.Rows.Add(4, "杨明", "男", "硕士");
dt.Rows.Add(5, "张德", "男", "本科");
return dt;
}
}