DataTable选择方法未返回任何值
本文关键字:返回 任何值 方法 选择 DataTable | 更新日期: 2024-09-22 11:23:42
我想根据switch表达式的值来检查数据表中的值是否存在。首先,我已经从数据库中加载了数据表。
SqlCommand cmd1 = new SqlCommand("Select mainMenuNum, subMenuData from [menudatas] where ivrNumber = '" + number + "';", objConnection);
SqlDataReader dataReader = cmd1.ExecuteReader();
DataTable dt = new DataTable();
dt.Load(dataReader);
在案例2中,我根据switch表达式的值检查datatable中是否存在记录。但它不起作用。
switch (number)
{
case 0: TextToSpeech("No information on 0 button"); break;
case 1: TextToSpeech("Hello"); break;
case 2:
{
DataRow[] result = dt.Select("subMenuData where mainMenuNum = '" +number + "'");
if (result != null)
{ LowerMenu();
break;
}
else
{
SqlCommand cmd = new SqlCommand("Select mainMenuData from [menudatas] WHERE mainMenuNum = '" + number + "' AND ivrNumber = '" + number + "'; ", objConnection);
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
data = dr.GetString(0);
}
dr.Close();
data1 = data;
objConnection.Close();
TextToSpeech(data1); break;
}
}
}
请帮我解决这件事。感谢
只需编写WHERE条件,不包含WHERE关键字或任何其他信息
DataRow[] result = dt.Select("mainMenuNum = '" +number + "'");
此时,结果数组包含与筛选器条件匹配的行。您可以使用检查行的内容
// Check if the result contains at least one row
if(result.Length > 0)
{
....
// if your logic requires another check on the returned columns you
// could add it to the Select expression above or just add a check here
// Here an example with a column of string type
if(result[0].Field<string>("YourColumnName") == "value")
....
....
}
您可以在MSDN 的DataColumn.expression属性页中找到要在Select
方法中使用的表达式的规则