创建登录，使用mysql server 5.7.14和工作台6.3和c#窗体应用程序

我正试图对正在进入我的应用程序的用户进行检查(登录)。我分别做了一个名为"mydb"，"雇员"的数据库和表。我已经在employee表的uname和password列中输入了用户名和密码。我要做的是，用户输入的用户名和密码是否有效?它的意思是它是否存在于表employee中?如果是允许访问，如果不是拒绝访问。为此，我使用visual studio 2013 ultimate在我的c#窗口窗体应用程序中编写了以下代码:

try
{
    string myconnection = "datasource=localhost; port=3306; username=root; password=shaban;  ";
    MySqlCommand selectcommand = new MySqlCommand(" slect * from mydb.employee where uname= "+this.username_txt.Text+" and pasword = "+this.pasword_txt.Text+"", myconn);
    MySqlDataReader myreader;
    myconn.Open();
    myreader = selectcommand.ExecuteReader();
    int count = 0;
    while (myreader.Read())
    { 
       count = count + 1; 
    }
    if (count == 1)
    { 
        MessageBox.Show("username and pasword is correct"); 
    }
    else if (count > 1)
    { 
        MessageBox.Show("Duplicate username and password...! Access Denied "); 
    }
    else 
    { 
        MessageBox.Show(" username and pasword not existing.. Try again" ); 
    }
    myconn.Close();
}
catch (Exception ex)
{    
    MessageBox.Show(ex.Message);    
}