possible to convert string to GUID?

Question

I have a dropdownlist selection, selected value will be ID, type is GUID, currently my code for the select button is

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click

    Dim Selection As String = Nothing

    If Not DropDownList3.SelectedValue Is Nothing Then Selection = DropDownList3.SelectedValue

    Session("Selected") = Selection

End Sub

then I have

Dim ID is guid
ID = Session("Selected")

then i need to execute sql such as select * from .. where ID=.. Problem happens at ID = Session("Selected"), as ID is GUID, while Session("Selected") is string I wonder if there is a way to handle it? Thanks very much for help!

possible duplicate of [C#: Test if string is a guid without throwing exceptions?](http://stackoverflow.com/questions/104850/c-test-if-string-is-a-guid-without-throwing-exceptions) — TFD, Feb 24 '14 at 00:37

kryptonkal · Accepted Answer · 2014-02-28T09:48:45.853

3

Try this method:

GUID myGuid;
object myObj = Session("Selected");

if (myObj != null && Guid.TryParse(myObj.ToString(), out myGuid))
{
   //input is good, do stuff here
}
else
{
   //input is bad, handle error
}

I hope this helps. Good luck.

edited Feb 28 '14 at 09:48

answered Feb 24 '14 at 00:31

kryptonkal

874
8
23

I tried ID = Guid.Parse(Session("Selected")), but when debug has an error saying Value cannot be null. Parameter name: input ? – user3344443 Feb 24 '14 at 00:40
The first check if the session object is not null. If it is null, you will have to check the method where you are setting it. – kryptonkal Feb 24 '14 at 00:43
I guess the default value is null? At the beginning nothing is selected in dropdownlist. I guess if i set ID to be GUID type, then I have to set a not null defaulted value for dropdownlist? – user3344443 Feb 24 '14 at 00:45
You could set the initial value for the dd list to be null. When you are testing it, and its null, you know that it is the initial selection, 'Please select...' – kryptonkal Feb 24 '14 at 00:47
Much appreciated for your help! – user3344443 Feb 24 '14 at 00:52
NP. Good luck coding! – kryptonkal Feb 24 '14 at 00:53

possible to convert string to GUID?

1 Answers1