C＃訪問數據庫查詢

Question

我在ms訪問中創建了數據庫，它有GPA列。 在列表框2中，我需要列出GPA大於2的學生。 我該怎麼做？

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

如果可以的話幫助。

Answer 1

我不知道這只是你發佈的僞代碼。但是，如果沒有，您正在閱讀DataReader，該文件或者未初始化，或者未使用正確的Command -sql，因爲您在前一行設置了CommandText。

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...... 
}