Cannot convert type 'System.Web.UI. Control' to ...

[Assimalyst]

Hi,

I am trying to write some server side validator code in C#. I want to
have a piece of code that can be used by all DropDownLists on a
webform, giving a false value if the SelectedIndex is 0.

Here's the code:

protected void serverValidateC boBx(object source,
ServerValidateE ventArgs args)
{
DropDownList dl =
FindControl(((C ustomValiator)( source)).Contro lToValidate);

if(dl.SelectedI ndex == 0)
{
args.IsValid = false;
}
else
{
args.IsValid = true;
}
}

But i get the build error

Cannot implicitly convert type 'System.Web.UI. Control' to
'System.Web.UI. WebControls.Dro pDownList'

and the FindControl syntax is underlined.

Any suggestions on ways to solve this?

Thanks

[Octavio Hernandez]

Hi,

FindControl returns a Control, you need a cast into a DropDownList (if you
know it's gonna be a DroDownList):

DropDownList dl = (DropDownList)
FindControl(((C ustomValiator)( source)).Contro lToValidate);

Regards - Octavio

"Assimalyst " <c_******@hotma il.com> escribió en el mensaje
news:11******** *************@z 14g2000cwz.goog legroups.com...

Hi,

I am trying to write some server side validator code in C#. I want to
have a piece of code that can be used by all DropDownLists on a
webform, giving a false value if the SelectedIndex is 0.

Here's the code:

protected void serverValidateC boBx(object source,
ServerValidateE ventArgs args)
{
DropDownList dl =
FindControl(((C ustomValiator)( source)).Contro lToValidate);

if(dl.SelectedI ndex == 0)
{
args.IsValid = false;
}
else
{
args.IsValid = true;
}
}

But i get the build error

Cannot implicitly convert type 'System.Web.UI. Control' to
'System.Web.UI. WebControls.Dro pDownList'

and the FindControl syntax is underlined.

Any suggestions on ways to solve this?

Thanks

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

FindControl returns a Control, not a DropDownList , do this:

DropDownList dl =
FindControl(((C ustomValiator)( source)).Contro lToValidate) as DropDownList ;
Cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Assimalyst " <c_******@hotma il.com> wrote in message
news:11******** *************@z 14g2000cwz.goog legroups.com...

Hi,

I am trying to write some server side validator code in C#. I want to
have a piece of code that can be used by all DropDownLists on a
webform, giving a false value if the SelectedIndex is 0.

Here's the code:

protected void serverValidateC boBx(object source,
ServerValidateE ventArgs args)
{
DropDownList dl =
FindControl(((C ustomValiator)( source)).Contro lToValidate);

if(dl.SelectedI ndex == 0)
{
args.IsValid = false;
}
else
{
args.IsValid = true;
}
}

But i get the build error

Cannot implicitly convert type 'System.Web.UI. Control' to
'System.Web.UI. WebControls.Dro pDownList'

and the FindControl syntax is underlined.

Any suggestions on ways to solve this?

Thanks

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,
The problem with this , is that if the control returned is not a
DropDownList you will get an exception, if you use "as" you will get a null
value , which you can check for after.
cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Octavio Hernandez" <do****@danysof t.com> wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

Hi,

FindControl returns a Control, you need a cast into a DropDownList (if you
know it's gonna be a DroDownList):

DropDownList dl = (DropDownList)
FindControl(((C ustomValiator)( source)).Contro lToValidate);

Regards - Octavio

"Assimalyst " <c_******@hotma il.com> escribió en el mensaje
news:11******** *************@z 14g2000cwz.goog legroups.com...

Hi,

I am trying to write some server side validator code in C#. I want to
have a piece of code that can be used by all DropDownLists on a
webform, giving a false value if the SelectedIndex is 0.

Here's the code:

protected void serverValidateC boBx(object source,
ServerValidateE ventArgs args)
{
DropDownList dl =
FindControl(((C ustomValiator)( source)).Contro lToValidate);

if(dl.SelectedI ndex == 0)
{
args.IsValid = false;
}
else
{
args.IsValid = true;
}
}

But i get the build error

Cannot implicitly convert type 'System.Web.UI. Control' to
'System.Web.UI. WebControls.Dro pDownList'

and the FindControl syntax is underlined.

Any suggestions on ways to solve this?

Thanks

[Lewis Harvey]

Can you not pass in the type and use that to cast it?

Get its parent from the control and then cast it wil that.
Lewis
"Ignacio Machin ( .NET/ C# MVP )" <ignacio.mach in AT dot.state.fl.us > wrote
in message news:Ov******** ******@TK2MSFTN GP14.phx.gbl...

Hi,
The problem with this , is that if the control returned is not a
DropDownList you will get an exception, if you use "as" you will get a
null value , which you can check for after.
cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Octavio Hernandez" <do****@danysof t.com> wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

Hi,

FindControl returns a Control, you need a cast into a DropDownList (if
you know it's gonna be a DroDownList):

DropDownList dl = (DropDownList)
FindControl(((C ustomValiator)( source)).Contro lToValidate);

Regards - Octavio

"Assimalyst " <c_******@hotma il.com> escribió en el mensaje
news:11******** *************@z 14g2000cwz.goog legroups.com...

Hi,

I am trying to write some server side validator code in C#. I want to
have a piece of code that can be used by all DropDownLists on a
webform, giving a false value if the SelectedIndex is 0.

Here's the code:

protected void serverValidateC boBx(object source,
ServerValidateE ventArgs args)
{
DropDownList dl =
FindControl(((C ustomValiator)( source)).Contro lToValidate);

if(dl.SelectedI ndex == 0)
{
args.IsValid = false;
}
else
{
args.IsValid = true;
}
}

But i get the build error

Cannot implicitly convert type 'System.Web.UI. Control' to
'System.Web.UI. WebControls.Dro pDownList'

and the FindControl syntax is underlined.

Any suggestions on ways to solve this?

Thanks

[Assimalyst]

Thank you both.

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

You can do so, it's just that a casting does fail with an exception if the
casting can not be done, the "is" operator returns null, which you should
always check in this case anyway.
cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation
"Lewis Harvey" <as***@asdas.co m> wrote in message
news:O6******** ******@TK2MSFTN GP12.phx.gbl...

Can you not pass in the type and use that to cast it?

Get its parent from the control and then cast it wil that.
Lewis
"Ignacio Machin ( .NET/ C# MVP )" <ignacio.mach in AT dot.state.fl.us >
wrote in message news:Ov******** ******@TK2MSFTN GP14.phx.gbl...

Hi,
The problem with this , is that if the control returned is not a
DropDownList you will get an exception, if you use "as" you will get a
null value , which you can check for after.
cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Octavio Hernandez" <do****@danysof t.com> wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

Hi,

FindControl returns a Control, you need a cast into a DropDownList (if
you know it's gonna be a DroDownList):

DropDownList dl = (DropDownList)
FindControl(((C ustomValiator)( source)).Contro lToValidate);

Regards - Octavio

"Assimalyst " <c_******@hotma il.com> escribió en el mensaje
news:11******** *************@z 14g2000cwz.goog legroups.com...
Hi,

I am trying to write some server side validator code in C#. I want to
have a piece of code that can be used by all DropDownLists on a
webform, giving a false value if the SelectedIndex is 0.

Here's the code:

protected void serverValidateC boBx(object source,
ServerValidateE ventArgs args)
{
DropDownList dl =
FindControl(((C ustomValiator)( source)).Contro lToValidate);

if(dl.SelectedI ndex == 0)
{
args.IsValid = false;
}
else
{
args.IsValid = true;
}
}

But i get the build error

Cannot implicitly convert type 'System.Web.UI. Control' to
'System.Web.UI. WebControls.Dro pDownList'

and the FindControl syntax is underlined.

Any suggestions on ways to solve this?

Thanks

[Octavio Hernandez]

Ignacio,

If the CustomValidator is gonna be attached only to DropDownList controls,
you can tell for sure FindControl will return a DropDownList. In that case
the typecast is 100% safe.

Regards - Octavio

*************** *************** *************** *************** **+

"Ignacio Machin ( .NET/ C# MVP )" <ignacio.mach in AT dot.state.fl.us >
escribió en el mensaje news:Ov******** ******@TK2MSFTN GP14.phx.gbl...

Hi,
The problem with this , is that if the control returned is not a
DropDownList you will get an exception, if you use "as" you will get a
null value , which you can check for after.
cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Octavio Hernandez" <do****@danysof t.com> wrote in message
news:%2******** ********@TK2MSF TNGP10.phx.gbl. ..

Hi,

FindControl returns a Control, you need a cast into a DropDownList (if
you know it's gonna be a DroDownList):

DropDownList dl = (DropDownList)
FindControl(((C ustomValiator)( source)).Contro lToValidate);

Regards - Octavio

"Assimalyst " <c_******@hotma il.com> escribió en el mensaje
news:11******** *************@z 14g2000cwz.goog legroups.com...

Hi,

I am trying to write some server side validator code in C#. I want to
have a piece of code that can be used by all DropDownLists on a
webform, giving a false value if the SelectedIndex is 0.

Here's the code:

protected void serverValidateC boBx(object source,
ServerValidateE ventArgs args)
{
DropDownList dl =
FindControl(((C ustomValiator)( source)).Contro lToValidate);

if(dl.SelectedI ndex == 0)
{
args.IsValid = false;
}
else
{
args.IsValid = true;
}
}

But i get the build error

Cannot implicitly convert type 'System.Web.UI. Control' to
'System.Web.UI. WebControls.Dro pDownList'

and the FindControl syntax is underlined.

Any suggestions on ways to solve this?

Thanks