variable scope in c#

[Mike P]

I'm calling this procedure from a custom validator OnServerValidate
event. I keep getting the error :

Use of unassigned local variable 'DateFrom'

I'm new to c# so I'm not really sure about the syntax I'm using. But it
seems the problem is that the DateFrom and DateTo values get lost
somewhere between being initialised and the line if (DateFrom > DateTo).
Can anybody help me out?

public void ValidateDates(object sender,
System.Web.UI.WebControls.ServerValidateEventArgs value)
{
bool blnValid = false;
DateTime DateFrom, DateTo;
int intErrorCount = 0;

if (SelectLog.Items[0].Selected)
{

blnValid = true;
}
else
{
try
{
DateFrom = Convert.ToDateTime(DayFrom.SelectedItem.Value
+ "/" + MonthFrom.SelectedItem.Value + "/" +
YearFrom.SelectedItem.Value);
}
catch
{
intErrorCount += 1;
}

try
{
DateTo = Convert.ToDateTime(DayTo.SelectedItem.Value +
"/" + MonthTo.SelectedItem.Value + "/" + YearTo.SelectedItem.Value);
}
catch
{
intErrorCount += 2;
}

if (intErrorCount == 1)
{
valCustom.ErrorMessage = "Please enter a valid Date
From";
blnValid = false;
value.IsValid = blnValid;
return;
}
else if (intErrorCount == 2)
{
valCustom.ErrorMessage = "Please enter a valid Date To";
blnValid = false;
value.IsValid = blnValid;
return;
}
else if (intErrorCount == 3)
{
valCustom.ErrorMessage = "Please enter a valid Date From
and Date To";
blnValid = false;
value.IsValid = blnValid;
return;
}
else
{
if (DateFrom > DateTo)
{
valCustom.ErrorMessage = "The date in the Date To
field must be the same or later than the date in the Date From field";
blnValid = false;
}
else
{


blnValid = true;
}
}
}
value.IsValid = blnValid;
return;
}



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[Christof Nordiek]

Hi Mike,

Your problem is with definite assignment; that means, it's a compiletime
error in C# if you read a variable that could be not assigned at that time.
The Problem in your code is, that the combile doesn't consider possible
variable values in flow control, so it doesn't know that the statement
if(DateFrom > DateTo) is unreachable if the assignment DateFrom =
Convert.DateTime... does fail.
A solution would be to initally assign the varibles:

DateTime DateFrom = new DateTime(), DateTo = new DateTime();

with that your Code should succeed.

cn

"Mike P" <mrp@telcoelectronics.co.uk> schrieb im Newsbeitrag
news:O33LM$9PDHA.3088@TK2MSFTNGP10.phx.gbl...

> I'm calling this procedure from a custom validator OnServerValidate
> event. I keep getting the error :
>
> Use of unassigned local variable 'DateFrom'
>
> I'm new to c# so I'm not really sure about the syntax I'm using. But it
> seems the problem is that the DateFrom and DateTo values get lost
> somewhere between being initialised and the line if (DateFrom > DateTo).
> Can anybody help me out?
>
> public void ValidateDates(object sender,
> System.Web.UI.WebControls.ServerValidateEventArgs value)
> {
> bool blnValid = false;
> DateTime DateFrom, DateTo;
> int intErrorCount = 0;
>
> if (SelectLog.Items[0].Selected)
> {
>
> blnValid = true;
> }
> else
> {
> try
> {
> DateFrom = Convert.ToDateTime(DayFrom.SelectedItem.Value
> + "/" + MonthFrom.SelectedItem.Value + "/" +
> YearFrom.SelectedItem.Value);
> }
> catch
> {
> intErrorCount += 1;
> }
>
> try
> {
> DateTo = Convert.ToDateTime(DayTo.SelectedItem.Value +
> "/" + MonthTo.SelectedItem.Value + "/" + YearTo.SelectedItem.Value);
> }
> catch
> {
> intErrorCount += 2;
> }
>
> if (intErrorCount == 1)
> {
> valCustom.ErrorMessage = "Please enter a valid Date
> From";
> blnValid = false;
> value.IsValid = blnValid;
> return;
> }
> else if (intErrorCount == 2)
> {
> valCustom.ErrorMessage = "Please enter a valid Date To";
> blnValid = false;
> value.IsValid = blnValid;
> return;
> }
> else if (intErrorCount == 3)
> {
> valCustom.ErrorMessage = "Please enter a valid Date From
> and Date To";
> blnValid = false;
> value.IsValid = blnValid;
> return;
> }
> else
> {
> if (DateFrom > DateTo)
> {
> valCustom.ErrorMessage = "The date in the Date To
> field must be the same or later than the date in the Date From field";
> blnValid = false;
> }
> else
> {
>
>
> blnValid = true;
> }
> }
> }
> value.IsValid = blnValid;
> return;
> }
>
>
>
> *** Sent via Developersdex [url]http://www.developersdex.com[/url] ***
> Don't just participate in USENET...get rewarded for it!

[William F. Robertson, Jr.]

With C# if you assign something during a try block, it isn't guaranteed the
operation will perform, so the compiler thinks the DateFrom and DateTo
fields are unassigned.

I would suggest having a ConvertDate function that

private bool ConvertDate( string date, ref DateTime dt )
{
try
{
dt = Convert.ToDateTime( date );
}
catch
{
return false;
}
return true;
}

And then in you event handler:

if ( !ConvertDate( DayFrom.SelectedItem.Value + "/" +
MonthFrom.SelectedItem.Value + "/" + YearFrom.SelectedItem.Value,
DateFrom ) )
intErrorCount += 1;


and so on.

HTH,

bill






"Mike P" <mrp@telcoelectronics.co.uk> wrote in message
news:O33LM$9PDHA.3088@TK2MSFTNGP10.phx.gbl...

> I'm calling this procedure from a custom validator OnServerValidate
> event. I keep getting the error :
>
> Use of unassigned local variable 'DateFrom'
>
> I'm new to c# so I'm not really sure about the syntax I'm using. But it
> seems the problem is that the DateFrom and DateTo values get lost
> somewhere between being initialised and the line if (DateFrom > DateTo).
> Can anybody help me out?
>
> public void ValidateDates(object sender,
> System.Web.UI.WebControls.ServerValidateEventArgs value)
> {
> bool blnValid = false;
> DateTime DateFrom, DateTo;
> int intErrorCount = 0;
>
> if (SelectLog.Items[0].Selected)
> {
>
> blnValid = true;
> }
> else
> {
> try
> {
> DateFrom = Convert.ToDateTime(DayFrom.SelectedItem.Value
> + "/" + MonthFrom.SelectedItem.Value + "/" +
> YearFrom.SelectedItem.Value);
> }
> catch
> {
> intErrorCount += 1;
> }
>
> try
> {
> DateTo = Convert.ToDateTime(DayTo.SelectedItem.Value +
> "/" + MonthTo.SelectedItem.Value + "/" + YearTo.SelectedItem.Value);
> }
> catch
> {
> intErrorCount += 2;
> }
>
> if (intErrorCount == 1)
> {
> valCustom.ErrorMessage = "Please enter a valid Date
> From";
> blnValid = false;
> value.IsValid = blnValid;
> return;
> }
> else if (intErrorCount == 2)
> {
> valCustom.ErrorMessage = "Please enter a valid Date To";
> blnValid = false;
> value.IsValid = blnValid;
> return;
> }
> else if (intErrorCount == 3)
> {
> valCustom.ErrorMessage = "Please enter a valid Date From
> and Date To";
> blnValid = false;
> value.IsValid = blnValid;
> return;
> }
> else
> {
> if (DateFrom > DateTo)
> {
> valCustom.ErrorMessage = "The date in the Date To
> field must be the same or later than the date in the Date From field";
> blnValid = false;
> }
> else
> {
>
>
> blnValid = true;
> }
> }
> }
> value.IsValid = blnValid;
> return;
> }
>
>
>
> *** Sent via Developersdex [url]http://www.developersdex.com[/url] ***
> Don't just participate in USENET...get rewarded for it!

[Kevin Spencer]

I agree. However, I would assign a value of null to the variables, as they
will have values assigned to them, and initializing an instance of a class
would therefore waste processor cycles.

HTH,

Kevin Spencer
Microsoft FrontPage MVP
Internet Developer
[url]http://www.takempis.com[/url]
Big things are made up of
lots of Little things.

"Christof Nordiek" <cnordiek@amexus.com> wrote in message
news:bdsbjg$sgl$01$1@news.t-online.com...

> Hi Mike,
>
> Your problem is with definite assignment; that means, it's a compiletime
> error in C# if you read a variable that could be not assigned at that

time.

> The Problem in your code is, that the combile doesn't consider possible
> variable values in flow control, so it doesn't know that the statement
> if(DateFrom > DateTo) is unreachable if the assignment DateFrom =
> Convert.DateTime... does fail.
> A solution would be to initally assign the varibles:
>
> DateTime DateFrom = new DateTime(), DateTo = new DateTime();
>
> with that your Code should succeed.
>
> cn
>
> "Mike P" <mrp@telcoelectronics.co.uk> schrieb im Newsbeitrag
> news:O33LM$9PDHA.3088@TK2MSFTNGP10.phx.gbl...

> > I'm calling this procedure from a custom validator OnServerValidate
> > event. I keep getting the error :
> >
> > Use of unassigned local variable 'DateFrom'
> >
> > I'm new to c# so I'm not really sure about the syntax I'm using. But it
> > seems the problem is that the DateFrom and DateTo values get lost
> > somewhere between being initialised and the line if (DateFrom > DateTo).
> > Can anybody help me out?
> >
> > public void ValidateDates(object sender,
> > System.Web.UI.WebControls.ServerValidateEventArgs value)
> > {
> > bool blnValid = false;
> > DateTime DateFrom, DateTo;
> > int intErrorCount = 0;
> >
> > if (SelectLog.Items[0].Selected)
> > {
> >
> > blnValid = true;
> > }
> > else
> > {
> > try
> > {
> > DateFrom = Convert.ToDateTime(DayFrom.SelectedItem.Value
> > + "/" + MonthFrom.SelectedItem.Value + "/" +
> > YearFrom.SelectedItem.Value);
> > }
> > catch
> > {
> > intErrorCount += 1;
> > }
> >
> > try
> > {
> > DateTo = Convert.ToDateTime(DayTo.SelectedItem.Value +
> > "/" + MonthTo.SelectedItem.Value + "/" + YearTo.SelectedItem.Value);
> > }
> > catch
> > {
> > intErrorCount += 2;
> > }
> >
> > if (intErrorCount == 1)
> > {
> > valCustom.ErrorMessage = "Please enter a valid Date
> > From";
> > blnValid = false;
> > value.IsValid = blnValid;
> > return;
> > }
> > else if (intErrorCount == 2)
> > {
> > valCustom.ErrorMessage = "Please enter a valid Date To";
> > blnValid = false;
> > value.IsValid = blnValid;
> > return;
> > }
> > else if (intErrorCount == 3)
> > {
> > valCustom.ErrorMessage = "Please enter a valid Date From
> > and Date To";
> > blnValid = false;
> > value.IsValid = blnValid;
> > return;
> > }
> > else
> > {
> > if (DateFrom > DateTo)
> > {
> > valCustom.ErrorMessage = "The date in the Date To
> > field must be the same or later than the date in the Date From field";
> > blnValid = false;
> > }
> > else
> > {
> >
> >
> > blnValid = true;
> > }
> > }
> > }
> > value.IsValid = blnValid;
> > return;
> > }
> >
> >
> >
> > *** Sent via Developersdex [url]http://www.developersdex.com[/url] ***
> > Don't just participate in USENET...get rewarded for it!

>
>