连接必须有效并打开 c# Winform答案

【问题标题】：Connection must be valid and Open c# Winform连接必须有效并打开 c# Winform
【发布时间】：2016-08-31 07:24:33
【问题描述】：

我收到错误：

连接必须有效且打开 c# Winform。

这是我的代码，谁能帮忙看看下面的代码有什么问题？

public void NameSearch()
    {
        listBox1.Visible = true;

        try
        {
        String constring = "datasource=localhost;port=3306;Initial Catalog = 'svms'; username = svms; password =svms2016CPU";
        string query = "select * from studentinformation where StudLname='" + metroTextBox1.Text + "'";

        MySqlConnection conDataBase = new MySqlConnection(constring);
        MySqlCommand cmdDataBase = new MySqlCommand(query, conDataBase);
        MySqlDataReader myReader = cmdDataBase.ExecuteReader();

        while (myReader.Read())
        {
        string Lname = myReader.GetString(myReader.GetOrdinal("StudLname"));
        string Fname = myReader.GetString(myReader.GetOrdinal("StudFname"));
        string Mname = myReader.GetString(myReader.GetOrdinal("StudMname"));
        string nameResult = Lname + ", " + Fname + "  " + Mname;
        listBox1.Items.Add(nameResult);
        }
        conDataBase.Close();
    }
    catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

【问题讨论】：

conDataBase.Open()
Connection must be valid and open error的可能重复
MySqlConnection conDataBase = new MySqlConnection(constring); MySqlCommand cmdDataBase = new MySqlCommand(query, conDataBase); MySqlDataReader myReader = cmdDataBase.ExecuteReader(); conDataBase.Open();同样的错误。

标签： c# mysql winforms

【解决方案1】：

使用前没有打开连接，打开连接

conDataBase.Open();

【讨论】：

【解决方案2】：

阅读前打开conn：

conDataBase.Open();

喜欢：

    String constring = "datasource=localhost;port=3306;Initial Catalog = 'svms'; username = svms; password =svms2016CPU";
    string query = "select * from studentinformation where StudLname='" + metroTextBox1.Text + "'";

    MySqlConnection conDataBase = new MySqlConnection(constring);
    MySqlCommand cmdDataBase = new MySqlCommand(query, conDataBase);
    //
    conDataBase.Open();
    //
    MySqlDataReader myReader = cmdDataBase.ExecuteReader();

【讨论】：