怎么把json格式的字符串写入指定的json文件中

引入using
Newtonsoft.Json;
数据查询后填充到DataTable
,再转　JsonConvert.SerializeObject
简单例子：
DataTable
dt
=
new
DataTable();
DataColumn
dcName
=
new
DataColumn("Name");
DataColumn
dcAge
=
new
DataColumn("Age");
DataColumn
dcCity
=
new
DataColumn("City");
dt.Columns.Add(dcName);
dt.Columns.Add(dcAge);
dt.Columns.Add(dcCity);
for
(int
i
=
0;
i
<
10;
i++)
{
DataRow
dr
=
dt.NewRow();
dr[0]
=
"Name"
+
i;
dr[1]
=
"Age"
+
i;
dr[2]
=
"City"
+
i;
dt.Rows.Add(dr);
}
json
=
JsonConvert.SerializeObject(dt);