Question

我是C＃的新手，我已将其与Oracle11g连接并使用Visual Studio 2013作为工具。我试图显示一个名字＆＃39;查询返回到文本框但它既不显示错误消息也不显示输出。请帮我解决这个问题。谢谢......这是我的代码..

private void button1_Click(object sender, EventArgs e)
    {
        try
        {
            string oradb = "Data Source=ORCL;User Id=hr; Password=123;";
            OracleConnection conn = new OracleConnection(oradb);  // C#
            conn.Open();
            OracleCommand cmd = new OracleCommand();
            cmd.Connection = conn;
            cmd.CommandText = "select name from std where cgpa=2.82;";
            cmd.CommandType = CommandType.Text;
            OracleDataReader dr = cmd.ExecuteReader();
            dr.Read();
            textBox1.Text = dr.GetString(0);
             conn.Dispose();
        }
        catch (Exception ex) { MessageBox.Show("\n"+ex); }
    }

设置textBox1.Text = dr.GetString（0）; 它给了我附加的例外。

Answer 1

数组索引从索引0开始，而不是1.返回的字符串（如果有）位于

textBox1.Text = dr.GetString(0);

编写代码的更正确的方法如下

private void button1_Click(object sender, EventArgs e)
{
    try
    {
        string oradb = "Data Source=ORCL;User Id=hr; Password=123;";

        // Use the using statements around disposable objects....
        using(OracleConnection conn = new OracleConnection(oradb))
        using(OracleCommand cmd = new OracleCommand())
        {
             conn.Open();

             // These two parameters could be passed directly in the
             // OracleCommand constructor....
             cmd.Connection = conn;
             cmd.CommandText = "select name from std where cgpa=2.82;";

             // Again using statement around disposable objects
             using(OracleDataReader dr = cmd.ExecuteReader())
             {
                  // Check if you have a record or not
                  if(dr.Read())
                      textBox1.Text = dr.GetString(0);
             }
        }
    }
    catch (Exception ex) { MessageBox.Show("\n"+ex); }
}

如果您的代码只能返回一个包含单个列的记录，那么您可以使用性能更高的ExecuteScalar而无需构建OracleDataReader

 // Again using statement around disposable objects
 object result = cmd.ExecuteScalar();
 if(result != null)
     textBox1.Text = result.ToString();

输出未在C＃中的TextBox中显示

1 个答案: