Question

我想将从数据库获得的信息传递给标签。如何将信息传递到变量中。

我该怎么做？

    private void button1_Click(object sender, EventArgs e)
    {
        var numero = textBox1.Text;

        string connection_string = "datasource=xxx;port=111;username=xxx;password=xxx";
        string Query = "select * from xxx.lojass where nome =" + numero;
        MySqlConnection conDate = new MySqlConnection(connection_string);
        MySqlCommand cmdDate = new MySqlCommand(Query, conDate);
        MySqlDataReader myReader; 

        try
        {
            conDate.Open();
            myReader = cmdDate.ExecuteReader();
            MessageBox.Show("Conected");

            while (myReader.Read())
            {
                label1.Text

            }


        }

        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }

    }

Answer 1

正确的编码。下面的代码注释中的说明

private void button1_Click(object sender, EventArgs e)
{
    try
    {

        const connStr = "datasource=xxx;port=111;username=xxx;password=xxx"; // constant
        // Instead of "select *" select particular column(s), it will help with reader columns later
        var sql = "select column1 from xxx.lojass where nome = @1"; // you need to parameterize. Never push text box value directly into sql
        // important to use "using" to release resources
        using (var conn = new MySqlConnection(connStr))
        {
            using (var cmd = new MySqlCommand(sql, conn))
            {
                // assuming "nome" is string. If the value is other datatype - convert it
                // Better yet - create parameter where you explicitly specify mySql data type 
                cmd.Parameters.AddWithValue("@1", textBox1.Text); 
                conn.Open(); 
                using (var reader = cmd.ExecuteReader()) // Since single value expected another way doing it - ExecuteScalar
                {
                    // you only fill one single value, so makes sense to use IF, not WHILE
                    if (reader.Read()) 
                        label1.Text = reader["column1"].ToString();
                }
            }   
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

显示来自MySQL数据库的信息

1 个答案: