An empty text field still stores data in SQL Server, even columns in the table are not allowed.

Question

I ran into this problem when I click the "Save" button, when all the text fields are empty, label labels are displayed on all these labels. When I fill the last text box, leaving all the others empty, it saves the data in the database with empty rows.

How can I deal with this problem?

if (tbIDCardNum.Text.Trim() == "")
{
    lblStarIDCardNum.Visibility = Visibility.Visible;
}

if (tbFirstName.Text.Trim() == "")
{
    lblStarFirstName.Visibility = Visibility.Visible;
}

if (rbMale.IsChecked == false && rbFemale.IsChecked == false)
{
    lblStarGender.Visibility = Visibility.Visible;
}

if (tbDOB.Text == "")
{
    lblStarDOB.Visibility = Visibility.Visible;
}

if (tbDateOfJoining.Text == "")
{
    lblStarDOJ.Visibility = Visibility.Visible;
}

if (tbEducation.Text.Trim() == "")
{
    lblStarEducation.Visibility = Visibility.Visible;
}

if (tbCNIC.Text.Trim() == "")
{
    lblStarCNIC.Visibility = Visibility.Visible;
}

if (tbSalary.Text.Trim() == "")
{
    lblStarSalary.Visibility = Visibility.Visible;
}

if (tbAddress.Text.Trim() == "")
{
    lblStarAddress.Visibility = Visibility.Visible;
}

if (tbEmail.Text.Trim() == "")
{
    lblStarEmail.Visibility = Visibility.Visible;
}

if (tbContact1.Text.Trim() == "")
{
    lblStarContact.Visibility = Visibility.Visible;
}
else
{
    try
    {
        conn.Open();

        cmd.CommandText = "insert into teacher (tIDCardNum, tFirstName, tLastName,tGender, tDOB, tCNIC, tEducation, tSalary, tJoinedOn, tAddress, tEmail, tContact1, tContact2, tContact3,tStatus) values ('" + tbIDCardNum.Text.Trim() + "' , '" + tbFirstName.Text.Trim() + "' , '" + tbLastName.Text.Trim() + "' , '" + gender + "' , '" + tbDOB.Text + "', '" + tbCNIC.Text + "' , '" + tbEducation.Text + "' , '" + tbSalary.Text.Trim() + "' , '" + tbDateOfJoining.Text.Trim() + "' , '" + tbAddress.Text.Trim() + "', '" + tbEmail.Text + "' , '" + tbContact1.Text + "' , '" + tbContact2.Text + "' , '" + tbContact3.Text + "',1)";

        cmd.Connection = conn;
        cmd.ExecuteNonQuery();

        cmd.Clone();
        conn.Close();

        HideStars();
        Refresh();

        MessageBox.Show("Saved");
   }
   catch (Exception ex)
   {
       if (ex.Message.Contains("Violation of PRIMARY KEY constraint "))
       {
           conn.Close();
           MessageBox.Show(ex.Message);
       }
       else
       {
           MessageBox.Show(ex.Message);
       }
   }
}

Answer 1

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, , , :

private bool HasEmptyFields = false;

, , /, 'HasEmptyFields' true, :

private void ValidateField(TextBox textBox, Label label) {

    // check if the textbox actually is null - or empty (""), which is a difference
    // the nifty helper string.IsNullOrEmpty() will help with that
    var fieldIsEmpty = string.IsNullOrEmpty(textBox.Text.Trim());

    // next, based on if the field is empty,  set the visibility of the label
    // don't worry, this is fancy syntax for a simple if...then...else
    label.Visibility = fieldIsEmpty ? Visibility.Visible : Visibility.Hidden;

    if (fieldIsEmpty) {
        // ONLY if this field is actually null, or empty, we make sure to 
        // inform the rest of the code this occ
        HasEmptyFields = true;
    }
}

- :

ValidateField(tbIDCardNum, lblStarIDCardNum);
ValidateField(tbFirstName, lblStarFirstName);
// etc... continue doing this for all you fields

if (HasEmptyFields) {
    // ONLY if there is any field detected as being empty/null
    // we simply stop here (and skip the insert-into-db stuff)
    return;
} 

try 
{
    // if all fields indeed have a value, let's
    // continue with the insert-into-db stuff here

    conn.Open();
    ...
} 

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Answer 2

, , - . https://msdn.microsoft.com/en-us/library/5hbw267h%28VS.80%29.aspx?f=255&MSPPError=-2147217396