title: MySql error System.InvalidOperationException in windows application-c#
body: <p>I am getting the error:</p>
  
  <blockquote>
    <p>An unhandled exception of type 'System.InvalidOperationException'
    occurred in MySql.Data.CF.dll</p>
  </blockquote>
  
  <p>in my windows application program. </p>
  
  <p><strong>Below is my code.</strong> </p>
  
  <pre><code>In app.config:
  
  inside connectionStrings tag
  
  add name="ConnectionString"     
  connectionString="server=localhost;database=my_db;user=root;port=3306;
  password=mypwd;
  
  In LoginForms.cs 
  
  using System.Configuration; 
  using MySql.Data.MySqlClient; 
  
  namespace MySoftware 
  { 
  public partial class Login : Form 
  { 
  MySqlConnection conn; 
  public static int valid = 0; 
  public Login() 
  { 
  InitializeComponent(); 
  } 
  
  private void btnLogin_Click(object sender, EventArgs e) 
  { 
  var connectionString =   
  ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString; 
  conn = new MySqlConnection(connectionString); 
  conn.open(); 
  MySqlCommand cmd = new MySqlCommand();  
  cmd.CommandText = "Verify_Login"; 
  cmd.CommandType = CommandType.StoredProcedure; 
  cmd.Parameters.AddWithValue("@uname", textBox1.Text); 
  cmd.Parameters["@uname"].Direction = ParameterDirection.Input; 
  cmd.Parameters.AddWithValue("@pwd", textBox2.Text); 
  cmd.Parameters["@pwd"].Direction = ParameterDirection.Input; 
  cmd.Parameters.AddWithValue("@result", MySqlDbType.Int32); 
  cmd.Parameters["@result"].Direction = ParameterDirection.Output; 
  cmd.ExecuteNonQuery(); // At this line the error is thrown
  int valid = (int)(cmd.Parameters["@result"].Value); 
  } 
  } 
  } 
  
  Verify_Login is a stored procedure which is created in MySQL as below. 
  
  CREATE PROCEDURE `Verify_Login`(in uname varchar(20),in pwd varchar(20),out    
  result bool) 
  BEGIN 
  select count(*) into result from Login where uname=uname and password=pwd; 
  END 
  
  Could anyone please help me with this?
  </code></pre>
  
  <p></p>