Object reference not set to an instance of an object

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Hello, I am getting the error object reference is not set to a instance
I am creating a new customer in the combobox select method but in the button click I go to update the customer but I get an error where I am updating the customer object. The error is here in this btn click:

this exact code error:
Customer newCreatedCustomer = new Customer(currentUser.UserID, TextboxFirstName.Text,
TextboxLastName.Text, TextboxAddress.Text, TextboxCity.Text,
ComboboxState.SelectedValue.ToString(), TextboxZip.Text, TextEmailAddress.Text);
UsersDB.UpdateCustomer(newCreatedCustomer);

C#

private void BtnProfileEdit_Click(object sender, RoutedEventArgs e)
        {

            
            EnableControls();
            
            if (boolBtnPush == true)
            {
                if (BtnProfileEdit.Content.Equals("Save"))                
                {
                    if(boolIsCustomer == true)                    
                    {
                        if (TextboxFirstName.Text.Equals(""))
                        {   
                            MessageBox.Show("You 'MUST' enter a First name,", "WARNING", MessageBoxButton.OK);
                        }
                        else
                        {
                            try
                            {                                
                                Customer newCreatedCustomer = new Customer(currentUser.UserID, TextboxFirstName.Text,
                                    TextboxLastName.Text, TextboxAddress.Text, TextboxCity.Text,
                                    ComboboxState.SelectedValue.ToString(), TextboxZip.Text, TextEmailAddress.Text);
                                UsersDB.UpdateCustomer(newCreatedCustomer);

                                
                            }
                            catch (Exception ex) { MessageBox.Show(ex.Message.ToString()); }
                        }
                    }
                    else
                    {
                        MessageBox.Show("You must select 'Yes' in combobox Customer\n" +
                            "to add customer data.", "UnAcceptable", MessageBoxButton.OK);
                    }                  
                }
            }
            //ON THE FIRST BUTTON CLICK DO THIS SO ON SECOND ABOVE CODE IS EXECUTED.
            boolBtnPush = true;
            BtnProfileEdit.Content = "Save";
        }

       
        private void CboCustomer_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            string cboValue = "";
            if (CboCustomer.SelectedIndex > 0)
                cboValue = ((ComboBoxItem)CboCustomer.SelectedItem).Content.ToString();
                
            if(cboValue.Equals("Yes"))          
            {
                boolIsCustomer = true;
                User addCustomer = null;
                Customer newCustomer = null;

                MessageBoxResult result = MessageBox.Show("Updating database to customer status.",
                    "Customer Confirmation", MessageBoxButton.YesNo, MessageBoxImage.Exclamation);
                if (result == MessageBoxResult.Yes)
                {
                    try
                    {
                        addCustomer = new User(currentUser.UserID, currentUser.Username,
                            currentUser.Password, currentUser.IsAdmin, currentUser.UserCreatedDate, boolIsCustomer);
                        UsersDB.UpdateCurrentUser(addCustomer);
                        //Create New Customer
                        newCustomer = new Customer(currentUser.UserID, currentUser.Username, null, null,
                                                    null, null, null, null);
                        UsersDB.CreateCustomer(newCustomer);
}
                    catch (Exception ex) { MessageBox.Show(ex.Message.ToString()); }
                }
                //else
                   // boolIsCustomer = false;
            }
        }

What I have tried:

making new object different ways putting this code in other sections

Posted 11-Nov-18 12:21pm

TheBigBearNow

Updated 11-Nov-18 21:30pm

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Aydin Homay · Accepted Answer · 2018-11-11T21:30:00

Hi I am more suspicious to the below line:
ComboboxState.SelectedValue.ToString()

Could you please do a favor and re-write your code in this way:

C#

var userId = currentUser.UserID;
var firstName = TextboxFirstName.Text;
var lastName = TextboxLastName.Text;
var address = TextboxAddress.Text;
var city = TextboxCity.Text;
var state = ComboboxState.SelectedValue.ToString();
var zip = TextboxZip.Text;
var email = TextEmailAddress.Text;

Customer newCreatedCustomer = new Customer(userId, firstName,
lastName, address,city,
state, zip, email);
UsersDB.UpdateCustomer(newCreatedCustomer);

This is more traceable because you can simply put a breakpoint at the first line and go step-by-step with F10 (if you are using MS-VS) and find out where is the problem. Somewhere you are running an action on a null object. For example: if the ComboboxState.SelectedValue is null then that line will throw null reference object error due to conversion to a string.

Cheers,
AH