Check for empty cookie

Question

User1510859543 posted

I am getting the following exception errors in some asp.net pages when converting value from a cookie.

"Input string was not in a correct format."

Below is a sample of code in Page_Load that is giving this error.

            Dim intPatientID As Int32 = 0
            If Request.Cookies("PatientID") Is Nothing Then
                'no PatientID cookie so see if valid logged in user
                If Not Request.Cookies("OrgID") Is Nothing Then
                    Response.Redirect("~/Ketohome.aspx?msg=Please select a Client first.")
                Else
                    'not logged in user
                    Response.Redirect("~/KetoStart.aspx")
                End If
            Else
                intPatientID = Convert.ToInt32(Request.Cookies("PatientID").Value)
            End If

The error happens in the next to last line above when I try to convert the value in a cookie.  Not sure if the cookie is empty that may be causing this but would like someone's input on how to best handle.  Thanks.

Answer 1

User-484054684 posted

If you pass the non-number data to Convert.ToInt32, we have chances to get this exception.

So, you can use Int32.TryParse method as in this MSDN article: http://msdn.microsoft.com/en-us/library/f02979c7.aspx?cs-save-lang=1&cs-lang=vb#code-snippet-1

Answer 2

User1176121428 posted

Hi  dlchase,

Thanks for your post.

I suggest that you can try check the cookies if it is null,like this:

If Request.Cookies("PatientID") IsNot Nothing Then
 //
End If

Hope this can be helpful.

Best Regards,

Eileen

Answer 3

User1510859543 posted

Will that work if the cookie value = "" (empty string)?

Why is that different from below which I am using?

If Request.Cookies("PatientID") Is Nothing Then

End If

Answer 4

User724169276 posted

Will that work if the cookie value = "" (empty string)?

Why is that different from below which I am using?

If Request.Cookies("PatientID") Is Nothing Then

End If

Before converting the patientid cookie, can you check whether it is having a valid integer number or not ?

intPatientID = Convert.ToInt32(Request.Cookies("PatientID").Value)

Answer 5

User1510859543 posted

I am experimenting with something like below.

                Dim intResult As Integer
                If Int32.TryParse(Request.Cookies("PatientID").Value, intResult) = True Then
                    txtDietType.Text = ClientsClass.DietType(Request.Cookies("PatientID").Value)
                End If

Answer 6

User-484054684 posted

Hi

As mentioned above, you get the Format exception, when the integer (number) is not passed to convert. 

So you can use Int32.TryParse as suggested above. 

http://msdn.microsoft.com/en-us/library/f02979c7.aspx?cs-save-lang=1&cs-lang=vb#code-snippet-1 

You can handle the logic based on true or false returned by above method. If it is true, it is valid integer, if it is false then there is some error with the value passed in.

Answer 7

User724169276 posted

I am experimenting with something like below.

                Dim intResult As Integer
                If Int32.TryParse(Request.Cookies("PatientID").Value, intResult) = True Then
                    txtDietType.Text = ClientsClass.DietType(Request.Cookies("PatientID").Value)
                End If

I am not sure about clientclass.diettype but is it going nside the if block ?

Answer 8

User1510859543 posted

This is an example of what I was doing on another page.  Our web app is setting the cookie value and can only be an integer as it comes from an identity column in an SQL table.  I was getting an exception error as mentioned previously and wanted to handle all conditions.  There is no place for the user to enter this value but I am guessing that the cookie becomes expired and maybe no longer there.

Answer 9

User-484054684 posted

You may check what is this value "Request.Cookies("PatientID").Value" appearing when debugging. That should give some clue if you are getting cookie value or not.

Also as Ashim has suggested, you may also need to cross check the other method you are invoking.

Answer 10

User724169276 posted

If String.IsNullOrEmpty(Request.Cookies("PatientID").Value) Then 
         //"is null or empty" 
      Else 
         If Int32.TryParse(Request.Cookies("PatientID").Value, intResult) = True Then
           txtDietType.Text = ClientsClass.DietType(Request.Cookies("PatientID").Value)
         End If
      End If 

I hope now you will get the output