Question

public void doTry()
        {
            db.ConnectionCheck();
            string sqlUname = "";
            string oracleUname = "";
            string usertesting = "select * from nayatable";
            db.cmd = new SqlCommand(usertesting, db.DBconnect);
            SqlDataReader myReader = db.cmd.ExecuteReader();
            if (myReader.Read())
            {
                sqlUname = myReader["USERNAME"].ToString();
                //MessageBox.Show(uname);
                textBox1.Text = sqlUname;
            }
    }

它只给出第一行第二个值，但我需要数据库中所有可用的列。

Answer 1

这里有很多选项，您可以按照Ehsan的说法使用DataTable，也可以使用List来收集所有数据。像这样：

public class dbLogin
{
   public string userName{get;set;}
}

public void doTry()
    {
        db.ConnectionCheck();
        string sqlUname = "";
        string oracleUname = "";
        string usertesting = "select * from nayatable";
        db.cmd = new SqlCommand(usertesting, db.DBconnect);
        SqlDataReader myReader = db.cmd.ExecuteReader();

List<dbLogin> dbData=new List<dbLogin>();


 if (myReader.Read())
        {
            dbLogin _dbLogin=new dbLogin();
            _dbLogin.userName = myReader["USERNAME"].ToString();
            textBox1.Text = sqlUname;
            dbData.Add(_dbLogin);
        }
}

Answer 2

如果要获取所有值，则必须 loop ：

        ...
        // Keep Sql Readable
        // Do not fetch unwanted columns - * 
        string userTesting = 
          @"select UserName 
              from NayaTable";

        // Wrap IDisposable into using
        using (db.cmd = new SqlCommand(userTesting, db.DBconnect)) {
          // Wrap IDisposable into using
          using(SqlDataReader myReader = db.cmd.ExecuteReader()) {
            // we are going to build one string from many records
            StringBuilder sb = new StringBuilder();

            // Here, we have to loop and aggregate / collect all the records
            while (myReader.Read()) {
              if (sb.Length > 0)
                sb.Append(", "); // delimiter 

              sb.Append(Convert.ToString(myReader["USERNAME"])); 
            }

            // Here you'll get usernames like "Sam, John, Mary" 
            textBox1.Text = sb.ToString(); 
          }
        }

如何从数据库表中获取C＃中的所有列值

2 个答案: