C＃访问数据库查询

Question

我在ms访问中创建了数据库，它有GPA列。 在listbox2中，我需要列出哪些GPA大于2的学生。我怎么做？

command.CommandText = "SELECT * FROM Student WHERE GPA > 2";
while (reader.Read())
{
  listBox2.Items.Add............?
}

如果可以，请帮助。

Answer 1

我不知道这是否只是你发布的伪代码。 但如果没有，您正在读取一个DataReader ，该DataReader未初始化或未使用正确的Command -sql，因为您之前将CommandText设置为一行。

command.CommandText = "SELECT * FROM Student WHERE GPA > 2";
using(var reader = command.ExecuteReader())
{
    while (reader.Read())
    {
        // assuming that there's a column with name: StudentName
        listBox2.Items.Add(reader.GetString(reader.GetOrdinal("StudentName")));
    }
}

Answer 2

string ConnectionString = "PUT YOU CONNECTION STRING HERE";

con = new SqlConnection(ConnectionString);
con.Open();
string CommandText = "SELECT * FROM Student WHERE GPA > 2";
cmd = new SqlCommand(CommandText);
cmd.Connection = con;
rdr = cmd.ExecuteReader();
lbx.Items.Clear();
while (rdr.Read())
{    
     lbx.Items.Add......
}