Check out the following blog:
http://codewidgets.blogspot.com/2008/05/what-you-did-not-know-about-structs-in.html
If you use the constructor - new TableFields() - it will initialize
all values to their default value. If you skip the constructor, you
have to initialize all members yourself.
On Aug 31, 7:58 pm, Benj Nunez <[EMAIL PROTECTED]> wrote:
> Hello experts,
>
> I recently deployed a project that uses
> a struct and is declared like this:
>
> struct TableFields
> {
> public string BadgeNumber;
> public string SSN;
> public string Name;
> }
>
> I have 4 methods that use this structure
> as a reference parameter. And these are:
>
> InsertRecord(ref TableFields stf)
> UpdateRecord(ref TableFields stf)
> getRecord(string ABadgeNumber, ref TableFields stf)
> getRecordEx(string ASSN, ref TableFields stf)
>
> The structure as well as the 4 methods are in a
> file called 'DatabaseManager'. The struct is
> declared outside the class.
>
> My MainForm.cs file uses the methods defined in the
> DatabaseManager.cs file.
>
> I have a btnSave_Click() event that uses the structure
> to temporarily store the contents of the textboxes like
> so:
>
> TableFields tblUser; // notice that no instantiation took place.
>
> tblUser.BadgeNumber = SearchbADGENUMBERTextBox.Text;
> tblUser.SSN = sSNTextBox.Text.ToUpper();
> tblUser.Name = nAMETextBox.Text;
>
> ... // validation / search for record if exists go here...
>
> dm.InsertRecord(tblUser);
>
> Now, here's what my validation code looks like:
>
> TableFields field = new TableFields(); // compile error when
> "new ..." is removed.
> if (dm.getRecord(SearchbADGENUMBERTextBox.Text.Trim(), field))
> {
> MessageBox.Show("Record with BadgeNumber " +
> SearchbADGENUMBERTextBox.Text + " already exists.",
> "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
> ...
>
> }
>
> The compiler error I get is:
>
> "Use of unassigned local variable 'field'"
>
> I just don't understand why at some point, the structure
> needs to be initialized prior to using it. Whereas, I was able
> to use the structure when I want to get the textbox.Text
> values. My assumption is that dm.getRecord might return null
> (since there's a sql call underneath it) and this might
> affect some of the structure's fields. Am I correct?
> Can someone enlighten me on this one? Thank you
> in advance.
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