Validations for textbox,Combobox in C#,Winforms

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C#

C#4.0

Hi,

i was applied validations for textboxes and comboxes using validated ,validating events and errorprovider
it's working fine.

but here the problem is:

i opened the form,and i kept the mouse on combobox or textbox ,without entering any if i click form's cancel (on top of form),

the form is not closed how to solve it.

Here is the code:

<pre lang="c#">using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
using System.Configuration;
using System.IO.Ports;


namespace Billling_Machine
{
    public partial class Connect : Form
    {
        String ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["myConnectionString"].ConnectionString;

       
        public Connect()
        {
            InitializeComponent();
        }

                       
        private void Connect_Load(object sender, EventArgs e)
        {
                        
            using (MySqlConnection con = new MySqlConnection(ConnectionString))
            {
                String query = "select machine_id from device";
                MySqlCommand command = new MySqlCommand(query,con);
                con.Open();
                MySqlDataAdapter da = new MySqlDataAdapter(query, con);
                DataTable dt = new DataTable();
                da.Fill(dt);
                DataRow dr = dt.NewRow();
                dr["machine_id"] = "Select";
                //dt.Rows.Insert(dr, 0);
                dt.Rows.InsertAt(dr,0);
                comboBox1.DataSource = dt;
                comboBox1.DisplayMember = "machine_id";
                comboBox1.ValueMember = "machine_id";
                comboBox1.SelectedIndex = 0;
 


            }

            string[] ArrayComPortsNames = null;
            int index = -1;
            string ComPortName = null;

            ArrayComPortsNames = SerialPort.GetPortNames();
            do
            {
                index += 1;
                comboBox2.Items.Add(ArrayComPortsNames[index]);
            }

            while (!((ArrayComPortsNames[index] == ComPortName)
                          || (index == ArrayComPortsNames.GetUpperBound(0))));
            Array.Sort(ArrayComPortsNames);

            //want to get first out
            if (index == ArrayComPortsNames.GetUpperBound(0))
            {
                ComPortName = ArrayComPortsNames[0];
            }
           // comboBox2.Text = ArrayComPortsNames[0];
            comboBox2.Text = "select";

        }

        private void btnconnect_Click(object sender, EventArgs e)
        {
            if (this.ValidateChildren(ValidationConstraints.Enabled))
            {
                try
                {
                    //get machine id into Form1
                    String value = comboBox1.SelectedValue.ToString();
                    Properties.Settings.Default.machineid = value;
                     serialPort1.PortName = comboBox2.SelectedItem.ToString();

                    Properties.Settings.Default.serialportname = serialPort1.PortName;
                    if (!serialPort1.IsOpen)
                    {
                        serialPort1.Open();
                        Properties.Settings.Default.portstatus = serialPort1.IsOpen;
                       
                    }

                    //get serialport status in Form1
                    //    bool value1 = serialPort1.IsOpen;
                    //     newform.portstatus = value1;
                    // this.Close();
                    //     newform.ShowDialog();
                    this.Hide();
                    Program.ConnectObj.Show();


                }
                catch (Exception q)
                {
                    MessageBox.Show("Unable To Open" + comboBox2.SelectedItem.ToString());
                }
            }
        }

        private void Connect_FormClosed(object sender, FormClosedEventArgs e)
        {
            Program.ConnectObj.Show();
           
        }

        private void Connect_FormClosing(object sender, FormClosingEventArgs e)
        {
            Program.ConnectObj.connect.Enabled = true;
            Program.ConnectObj.btnConnect.Enabled = true;
            Program.ConnectObj.btnDisconnect.Enabled = false;
            Program.ConnectObj.disconnect.Enabled = false;
            Program.ConnectObj.uploadToDevice.Enabled = false;
            Program.ConnectObj.downloadFromDevice.Enabled = false;
        }

        private void comboBox1_Validating(object sender, CancelEventArgs e)
        {
            bool cancel = false;
            if (comboBox1.SelectedIndex == -1)
            { 
             cancel = true;
                this.errorProvider1.SetError(this.comboBox1, "Select Machine ID");
            }
            e.Cancel = cancel;
            
           
        }

        private void comboBox1_Validated(object sender, EventArgs e)
        {
            this.errorProvider1.SetError(this.comboBox1, string.Empty);
        }

        private void comboBox2_Validating(object sender, CancelEventArgs e)
        {
            bool cancel = false;
            if (comboBox2.SelectedIndex == -1)
            {
                cancel = true;
                this.errorProvider1.SetError(this.comboBox2, "Select COM port");
            }
            e.Cancel = cancel;
            
        }

        private void comboBox2_Validated(object sender, EventArgs e)
        {
            this.errorProvider1.SetError(this.comboBox2, string.Empty);
        }

       
       
    }
}

and designer is:

<pre lang="c#">namespace Billling_Machine
{
    partial class Connect
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.components = new System.ComponentModel.Container();
            this.groupBox1 = new System.Windows.Forms.GroupBox();
            this.btnconnect = new System.Windows.Forms.Button();
            this.comboBox2 = new System.Windows.Forms.ComboBox();
            this.label1 = new System.Windows.Forms.Label();
            this.comboBox1 = new System.Windows.Forms.ComboBox();
            this.label2 = new System.Windows.Forms.Label();
            this.serialPort1 = new System.IO.Ports.SerialPort(this.components);
            this.errorProvider1 = new System.Windows.Forms.ErrorProvider(this.components);
            this.groupBox1.SuspendLayout();
            ((System.ComponentModel.ISupportInitialize)(this.errorProvider1)).BeginInit();
            this.SuspendLayout();
            // 
            // groupBox1
            // 
            this.groupBox1.Controls.Add(this.btnconnect);
            this.groupBox1.Controls.Add(this.comboBox2);
            this.groupBox1.Controls.Add(this.label1);
            this.groupBox1.Controls.Add(this.comboBox1);
            this.groupBox1.Controls.Add(this.label2);
            this.groupBox1.Font = new System.Drawing.Font("Times New Roman", 9.75F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.groupBox1.Location = new System.Drawing.Point(58, 42);
            this.groupBox1.Name = "groupBox1";
            this.groupBox1.Size = new System.Drawing.Size(326, 175);
            this.groupBox1.TabIndex = 0;
            this.groupBox1.TabStop = false;
            this.groupBox1.Text = "Enter";
            // 
            // btnconnect
            // 
            this.btnconnect.DialogResult = System.Windows.Forms.DialogResult.Cancel;
            this.btnconnect.Font = new System.Drawing.Font("Times New Roman", 12F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.btnconnect.Location = new System.Drawing.Point(96, 125);
            this.btnconnect.Name = "btnconnect";
            this.btnconnect.Size = new System.Drawing.Size(75, 23);
            this.btnconnect.TabIndex = 13;
            this.btnconnect.Text = "Connect";
            this.btnconnect.UseVisualStyleBackColor = true;
            this.btnconnect.Click += new System.EventHandler(this.btnconnect_Click);
            // 
            // comboBox2
            // 
            this.comboBox2.Font = new System.Drawing.Font("Times New Roman", 9.75F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.comboBox2.FormattingEnabled = true;
            this.comboBox2.Location = new System.Drawing.Point(143, 76);
            this.comboBox2.Name = "comboBox2";
            this.comboBox2.Size = new System.Drawing.Size(121, 23);
            this.comboBox2.TabIndex = 12;
            this.comboBox2.Text = "Select";
            this.comboBox2.Validating += new System.ComponentModel.CancelEventHandler(this.comboBox2_Validating);
            this.comboBox2.Validated += new System.EventHandler(this.comboBox2_Validated);
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Font = new System.Drawing.Font("Times New Roman", 11.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.label1.Location = new System.Drawing.Point(29, 82);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(78, 17);
            this.label1.TabIndex = 11;
            this.label1.Text = "COM Port";
            // 
            // comboBox1
            // 
            this.comboBox1.Font = new System.Drawing.Font("Times New Roman", 12F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.comboBox1.FormattingEnabled = true;
            this.comboBox1.Location = new System.Drawing.Point(143, 42);
            this.comboBox1.Name = "comboBox1";
            this.comboBox1.Size = new System.Drawing.Size(121, 27);
            this.comboBox1.TabIndex = 10;
            this.comboBox1.Text = "Select";
            //this.comboBox1.SelectedIndexChanged += new System.EventHandler(this.comboBox1_SelectedIndexChanged);
            this.comboBox1.Validating += new System.ComponentModel.CancelEventHandler(this.comboBox1_Validating);
            // 
            // label2
            // 
            this.label2.AutoSize = true;
            this.label2.Font = new System.Drawing.Font("Times New Roman", 11.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.label2.Location = new System.Drawing.Point(29, 43);
            this.label2.Name = "label2";
            this.label2.Size = new System.Drawing.Size(86, 17);
            this.label2.TabIndex = 9;
            this.label2.Text = "Machine ID";
            // 
            // errorProvider1
            // 
            this.errorProvider1.ContainerControl = this;
            // 
            // Connect
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(458, 266);
            this.Controls.Add(this.groupBox1);
            this.Name = "Connect";
            this.Text = "Connect";
            this.FormClosing += new System.Windows.Forms.FormClosingEventHandler(this.Connect_FormClosing);
            this.FormClosed += new System.Windows.Forms.FormClosedEventHandler(this.Connect_FormClosed);
            this.Load += new System.EventHandler(this.Connect_Load);
            this.groupBox1.ResumeLayout(false);
            this.groupBox1.PerformLayout();
            ((System.ComponentModel.ISupportInitialize)(this.errorProvider1)).EndInit();
            this.ResumeLayout(false);

        }

        #endregion

        private System.Windows.Forms.GroupBox groupBox1;
        private System.Windows.Forms.Button btnconnect;
        private System.Windows.Forms.ComboBox comboBox2;
        private System.Windows.Forms.Label label1;
        public System.Windows.Forms.ComboBox comboBox1;
        private System.Windows.Forms.Label label2;
        public System.IO.Ports.SerialPort serialPort1;
        private System.Windows.Forms.ErrorProvider errorProvider1;
    }
}