C# wpf bcrypt verification via sql server table

Question

private void UserInputKeyDown(object sender, KeyEventArgs e)
{
 if (e.Key == Key.Enter) //only accepts enter key
 {
  string dbconnection = ConfigurationManager.ConnectionStrings["OverwatchDatabase"].ConnectionString;
  SqlConnection connection = new SqlConnection(dbconnection);
  connection.Open();
  if (connection.State == ConnectionState.Open)
  {
   MessageBox.Show("You have been successfully connected to the database!");
   SqlCommand Password_Hash = new SqlCommand("SELECT Password_Hash" + "From dbo.Authorized_Personnel", connection); //Password_Hash is the column name and Authorized_Personnel is the tables name
   bool Authenticate = BCrypt.Net.BCrypt.Verify(UserInput.Password, Password_Hash);  //UserInput.Password is the password box on my wpf application
   if (Authenticate == true)
   {
    MessageBox.Show("Authentication Successful");
    connection.Close(); //closes the connection to database
    mainscreen = new MainScreen();
    mainscreen.Show();
    this.Close();
   }
   else
   {
    MessageBox.Show("Authentication Failed");
    Application.Current.Shutdown();
   }
  }
  else
  {
    MessageBox.Show("Connection failed.");
  }
 }
}

I'm having trouble authenticating against my sql server with bcrypt if anyone can help and explain what going on that would very much appreciated  

 

 its throwing an error at the moment saying cannot convert system.dat.sqlclinet.sqlcommand to string