input string was not in a correct format?

Hi,

I have created an .aspx web page as a front-end form to my db table with the below code for an input field:

<div class="regText">
            <asp:TextBox ID="tbxHowMany" runat="server"></asp:TextBox>
            <asp:CompareValidator ID="cv" runat="server" ControlToValidate="tbxHowMany" Type="Integer" 
             Operator="DataTypeCheck" ErrorMessage="Value must be an integer" />
        </div>

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The database field is of type integer and is set to null.

The code behind looks like:

ql.Learners = Convert.ToInt32(tbxHowMany.Text);

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The above field is not a required field, hence the null reference. However, upon testing the form the error "input string was not in a correct format" flags on submit. How can I alter my code to allow the form to accept a null value on submit?

Thanks.
aspnet-scotlandAsked:
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Chinmay PatelChief Technical NinjaCommented:
Hi aspnet-scotland,

Try this

if(!string.IsNullOrEmpty(tbxHowMany.Text))
{
ql.Learners = Convert.ToInt32(tbxHowMany.Text);
}

You may also want to put a validation for numeric input on the Textbox.

Regards,
Chinmay.

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aspnet-scotlandAuthor Commented:
Do I not already have that validation...

<asp:CompareValidator ID="cv" runat="server" ControlToValidate="tbxHowMany" Type="Integer" 
             Operator="DataTypeCheck" ErrorMessage="Value must be an integer" />

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Chinmay PatelChief Technical NinjaCommented:
Sorry... my bad... was Tired n Hungry.. :D
käµfm³d 👽Commented:
Do I not already have that validation...
No, you do not. Please read up on the CompareValidator. From the linked page:

If the input control is empty, no validation functions are called and validation succeeds. Use a RequiredFieldValidator control to require the user to enter data in the input control.

Also, you have not specified the value to compare against. You should either be targeting a constant value or another input field. You would use a CompareValidator to say, "this field must be less than 5," or "this field must be greater than the value entered in txtSomeOtherValue." You have neither of these.
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