Question Object reference no set to an instance or object ?

[manny cash]

Hi People, blessings

I had create a teble, Primary, key 2 datetimepicker and the rest NVarchar. Now I have 2 button clicks, Add and Save, the fields and the textbox are the same. When I ran it, I got this error. I was looking with another programmer, and he and I couldn't fix it. In this case I need your help because you are experienced in programming. Here is a picture of my code. Thank you in advance, guys.

 

[jmcilhinney]

I specifically asked you in your last thread to not post pictures of code. Post the code as text, formatted as code. You can highlight one or more lines as well that way. You should then provide any error messages as appropriately formatted text as well. If we want to search the web for that error message, we shouldn't have to type it all out ourselves when you already have it. The same goes for code if we want to run it or provide an edited version. You can provide a screenshot in addition to the text, if it adds genuine value, but ALWAYS provide the text.

 

[jmcilhinney]

As for the issue, what the error message is telling you and you could have seen for yourself by simply mousing over the variable, is that txtEmail is Nothing. You can't get the Text of an object that doesn't exist. Either you have never actually created a control with that name and have simply declared a property manually, or you have explicitly assigned Nothing to txtEmail at some point. My guess would be that you intended to clear the Text at some point but you assigned Nothing to txtEmail instead of txtEmail.Text. That's an educated guess but you can just search for all usages of txtEmail to find out for yourself.

 

[manny cash]

I specifically asked you in your last thread to not post pictures of code. Post the code as text, formatted as code. You can highlight one or more lines as well that way. You should then provide any error messages as appropriately formatted text as well. If we want to search the web for that error message, we shouldn't have to type it all out ourselves when you already have it. The same goes for code if we want to run it or provide an edited version. You can provide a screenshot in addition to the text, if it adds genuine value, but ALWAYS provide the text.

OK, I understand now

 

[manny cash]

As for the issue, what the error message is telling you and you could have seen for yourself by simply mousing over the variable, is that txtEmail is Nothing. You can't get the Text of an object that doesn't exist. Either you have never actually created a control with that name and have simply declared a property manually, or you have explicitly assigned Nothing to txtEmail at some point. My guess would be that you intended to clear the Text at some point but you assigned Nothing to txtEmail instead of txtEmail.Text. That's an educated guess but you can just search for all usages of txtEmail to find out for yourself.

Hello Jmcilhinney, I did not read your message because I was out of the city. You say create a control for it. But I do not know how I can do that? The txtEmeil is a text box setting in the design from1. any example please I will check it up in my database table. Perhap that is the error. Thank you.

 

[Rythorian]

It sounds like you're hitting a common issue in programming when an object reference isn't pointing to a valid object. The error message "Object reference not set to an instance of an object" (which is the full text for the "txtEmail is Nothing" explanation you received) means you're trying to use a variable (txtEmail) that hasn't been properly created or assigned an object yet. In simpler terms, the variable exists, but it's currently empty or pointing to "nothing," and you can't get the .Text property of something that doesn't exist.

You mentioned that txtEmail is a TextBox you placed on your form using the designer. This is the standard way to create controls on a Windows Form. When you drag and drop a TextBox onto the form in the design view and give it the name txtEmail, the Visual Studio designer automatically generates code in a hidden file (usually named YourFormName.Designer.vb) that does two main things:

1. Declares the variable: It declares a variable (usually WithEvents) for the TextBox control.
2. Initializes the object: It creates a new instance of the TextBox class and assigns it to that variable. This happens within the InitializeComponent method, which is called by your form's constructor (New).

Here's a simplified example of what you'd typically find in your Form1.Designer.vb file for txtEmail:

' 
Friend WithEvents txtEmail As System.Windows.Forms.TextBox

' (Other control declarations...)

<System.Diagnostics.DebuggerStepThrough()> _
Private Sub InitializeComponent()
    ' (Code to set up the form and other controls...)

    Me.txtEmail = New System.Windows.Forms.TextBox()

    ' (Code to set properties of txtEmail, like Location, Size, Name, etc.)
    Me.txtEmail.Location = New System.Drawing.Point(..., ...)
    Me.txtEmail.Name = "txtEmail"
    Me.txtEmail.Size = New System.Drawing.Size(..., ...)
    ' (Other properties...)

    ' (Code to add txtEmail to the form's Controls collection...)
    Me.Controls.Add(Me.txtEmail)

    ' (More setup code...)
End Sub

'

Even though the designer should handle this, here are the most common reasons why txtEmail might be Nothing when your code tries to access txtEmail.Text:

1. Control Deleted from Designer:You might have accidentally deleted the txtEmail TextBox from the form in the designer view. If you delete the control visually but the variable declaration (Friend WithEvents txtEmail As System.Windows.Forms.TextBox) remains in Form1.Designer.vb, the InitializeComponent method will no longer create and assign the TextBox object to txtEmail, leaving the variable as Nothing.
   • How to check: Open your form in the designer view and look for the TextBox you expect to be txtEmail. Check its Name property in the Properties window to confirm it's indeed named txtEmail. If it's not there, you'll need to add a new TextBox and name it txtEmail.
2. Issue with InitializeComponent:There might be an error in the InitializeComponent method in Form1.Designer.vb that is preventing the txtEmail object from being created and assigned. This is less common but can happen.
   • How to check: In the Solution Explorer, right-click on Form1.vb and select "View Code". Then, at the top of the code window, you might see a plus sign next to the form's class definition. Expand this to see the "Windows Form Designer generated code" region (this might vary slightly depending on your VS version and settings). Inside this region is the InitializeComponent method. Look for the line Me.txtEmail = New System.Windows.Forms.TextBox() and ensure it's present and doesn't have any errors associated with it. Also, confirm that txtEmail is declared as Friend WithEvents txtEmail As System.Windows.Forms.TextBox outside of any methods.
3. Explicitly Setting txtEmail = Nothing in Your Code: Somewhere in your own code (not the designer file), you might have a line that says txtEmail = Nothing. This would overwrite the valid object reference created by the designer. This often happens by mistake when you intendedto clear the text, i.e., txtEmail.Text = "".
   • How to check: Search your entire form's code (Form1.vb) for any lines where you are assigning a value directly to txtEmail. Make sure you are only assigning to txtEmail.Text.
4. Working with the Wrong Form Instance: If you are creating a new instance of Form1 in another part of your application's code (e.g., Dim myForm As New Form1()) and then trying to access myForm.txtEmail.Text before the form is shown or InitializeComponent is called, txtEmail on that newinstance might be Nothing depending on how you're doing it. However, if you're writing code directly within Form1.vb (like in a button click event handler on Form1), Me.txtEmail should be properly initialized when the form is created and shown.
   • How to check: Review the code that creates and displays your Form1. Ensure you are interacting with the same instance of the form that is being displayed and has its controls initialized.

Troubleshooting Steps to Follow:

1. Open Form1 in the Designer: Visually confirm that the TextBox named txtEmail exists on your form. If not, add a new one and set its Name property to txtEmail.
2. Examine Form1.Designer.vb: Open the designer file and verify the declaration of txtEmail and its initialization within InitializeComponent. Do not manually edit the designer file unless you are very careful, as it can cause issues with the designer.
3. Search Your Code: Use the Find feature in Visual Studio to search all code files in your project (or at least Form1.vb) for txtEmail =. See if you are accidentally setting the txtEmail variable itself to Nothing.
4. Set a Breakpoint: Place a breakpoint on the line where you get the error (e.g., the line trying to access txtEmail.Text). Run your application in debug mode. When the breakpoint is hit, hover your mouse cursor over txtEmail. The debugger tooltip will show you its current value, which will likely be Nothing. You can then step through your code line by line (using F10 or F11) leading up to that point to see where txtEmail might have become Nothing.

By following these steps, you should be able to pinpoint why your txtEmail variable is Nothing and correct the issue. Providing the actual code where the error occurs, as plain text, would also be very helpful for more specific guidance in the future.