validating textboxes

 i want error icon when each and every textboxes are empty

For example if txtcompanyname is empty when i click on submit button 

txtCompnayname textbox should pop up with message icon

please help me. 

thanks in advance 

private void btnSubmit_Click_1(object sender, EventArgs e)

{

{

string From = string.Empty;

string FromPWD = string.Empty;

string ToAddress = string.Empty;

string BCCAddress = string.Empty;

string Name = string.Empty;

string Phone = string.Empty;

string Email = string.Empty;

string Comments = string.Empty;

string ticket = string.Empty;

string MessageBody = string.Empty;

try

{

txtCompanyName.Focus();

string file2 = "test.txt";

FileInfo fiRead = new FileInfo(file2);

string input = string.Empty;

int num = 1;

if (fiRead.Exists)

{

input = File.ReadAllText(file2);

}

if (input != string.Empty)

{

num = Convert.ToInt32(input);

}

File.WriteAllText(file2, (num + 1).ToString());

{

MessageBox.Show(num.ToString(), "Your Ticket Number is");

txtticket.Text = num.ToString();

if (string.IsNullOrEmpty(txtCompanyName.Text.Trim()))

{

errorProvider1.SetError(txtCompanyName, "Name is required.");

}

else

{

errorProvider1.SetError(txtCompanyName, string.Empty);

errorProvider1.SetError(txtName, string.Empty);

errorProvider1.SetError(txtPhone, string.Empty);

errorProvider1.SetError(txtEmail, string.Empty);

errorProvider1.SetError(txtIssue, string.Empty);

errorProvider1.SetError(txtComments, string.Empty);

}

}

ConfirmLicenseManager objConfirmLicenseManager = new ConfirmLicenseManager();

DocSortResult getAllConfigValues = objConfirmLicenseManager.GetAllConfigValues();

if (getAllConfigValues.resultDS != null && getAllConfigValues.resultDS.Tables[0].Rows.Count > 0)

{

foreach (DataRow dr in getAllConfigValues.resultDS.Tables[0].Rows)

{

switch (Convert.ToString(dr["Config_Name"].ToString()).ToUpper())

{

case "FROMEMAIL":

From = (this.Decrypt(dr["Config_Value"].ToString()));

break;

case "FROMPASSWORD":

FromPWD = (this.Decrypt(dr["Config_Value"].ToString()));

break;

case "TOADDRESS":

ToAddress = dr["Config_Value"].ToString();

break;

case "BCCADDRESS":

BCCAddress = dr["Config_Value"].ToString();

break;

}

}

SmtpClient client = new SmtpClient("smtp.gmail.com");

client.Port = 587;

client.EnableSsl = true;

client.Timeout = 100000;

client.DeliveryMethod = SmtpDeliveryMethod.Network;

client.UseDefaultCredentials = false;

client.Credentials = new NetworkCredential(From, "");

MailMessage msg = new MailMessage();

msg.To.Add(ToAddress);

msg.Bcc.Add(BCCAddress);

msg.From = new MailAddress(From);

msg.Subject = "Application TicketScreen";

if (txtCompanyName.Text != "") CompanyName = txtCompanyName.Text.Trim();

if (txtName.Text != "") Name = txtName.Text.Trim();

if (txtPhone.Text != "") Phone = txtPhone.Text.Trim();

if (txtEmail.Text != "") Email = txtEmail.Text.Trim();

if (txtIssue.Text != "") Issue = txtIssue.Text.Trim();

if (txtComments.Text != "") Comments = txtComments.Text.Trim();

if (txtticket.Text != "") ticket = txtticket.Text.Trim();

{

}

string Message = "CompanyName: " + CompanyName + "\r\n" + "\r\n" + "Name: " + Name + "\r\n" + "\r\n" + "Phone: " + Phone + "\r\n" + "\r\n" + "Email: " + Email + "\r\n" + "\r\n" + "ticket: " + ticket + "\r\n" + "\r\n" + "Issue: " + Issue + "\r\n" + "\r\n" + "Comments: " + Comments;

msg.Body = Message;

//Attachment data = new Attachment(txtAttachments.Text);

//msg.Attachments.Add(data);

client.Send(msg);

TicketScreen objticketScreen = new TicketScreen();

}

}

catch (Exception ex)

{

MessageBox.Show(ex.Message);

}

txtCompanyName.Text = "";

txtName.Text = "";

txtPhone.Text = "";

txtEmail.Text = "";

txtComments.Text = "";

txtIssue.Text = "";

txtticket.Text = "";

this.Hide();

}

}

private readonly byte[] IVRegular = new byte[8] { 54, 17, 92, 36, 0, 18, 237, 152 };

public string Issue { get; private set; }

public string CompanyName { get; private set; }

private string Decrypt(string encryptedQueryString)

{

string EncryptionKey = "";

string methodName = "decrypt()";

try

{

byte[] buffer = null;

buffer = Convert.FromBase64String(encryptedQueryString);

TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();

MD5CryptoServiceProvider MD5 = new MD5CryptoServiceProvider();

des.Key = MD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(System.Configuration.ConfigurationSettings.AppSettings["SecurityKey"]));

des.IV = IVRegular;

EncryptionKey = Encoding.ASCII.GetString(des.CreateDecryptor().TransformFinalBlock(buffer, 0, buffer.Length));

}

catch (CryptographicException)

{

return "Invalid credentials";

// throw e;

//MessageBox.Show("Invalid LicenseKey", "Invalid LicenseKey");

}

catch (FormatException)

{

return "Invalid credentials";

//throw excp;

//MessageBox.Show("Invalid LicenseKey", "Invalid LicenseKey");

}

return EncryptionKey;

}

private void txtPhone_KeyPress(object sender, KeyPressEventArgs e)

{

lblErrorMsg.Visible = false;

if ((e.KeyChar >= 48 && e.KeyChar <= 57) || e.KeyChar == 8)

{

e.Handled = false;

}

else

{

lblErrorMsg.Visible = true;

lblErrorMsg.Text = "Please enter numbers only";

e.Handled = true;

}

}

private void TicketScreen_Load(object sender, EventArgs e)

{

this.Hide();

}

private void label8_Click(object sender, EventArgs e)

{

}