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Dynamic variable/object name reference. how to do in VB.NET?I have a form that has 10 dropdown lists in one section each of the dropdowns contain the same data what i'm looking to do is that when a user selects a value from one dropdown, change the value to null/nothing for any other dropdowns that may have had the same value as the one that was just selected. and have all the dropdowns use the same "selected index changed" code behind. so if ddl1 was changed, fire the code behind to sweep thru all the dropdowns and reset it if there was a match. was thinking of pseudo code for this would be something like.... assume all the dropdowns are named dd1,dd2,dd3,dd4,dd5,dd6,etc while I < 11 loop if newly selected value = "ddl"+I.selectedindex.text then "ddl"+I.selectedindex = 0 end if end loop in javascript there is a function eval() whose parameter is a string. so results of that call eval("string_to_evaluate") gets executed or interpreted as if you had type the string out directly. also, what would be the line of code to tell which dropdown the user changed and cause the codebehind to trigger? what I was calling "newly selected value" above thanks again for any help! simon wrote:
Show quoteHide quote > hello, Well you can do your "Eval" thing using reflection. Do a search on "get > I have a form that has 10 dropdown lists in one section > each of the dropdowns contain the same data > > what i'm looking to do is that when a user selects a value from one > dropdown, change the value to null/nothing for any other dropdowns > that may have had the same value as the one that was just selected. > and have all the dropdowns use the same "selected index changed" code > behind. > > so if ddl1 was changed, fire the code behind to sweep thru all the > dropdowns and reset it if there was a match. > > was thinking of pseudo code for this would be something like.... > assume all the dropdowns are named dd1,dd2,dd3,dd4,dd5,dd6,etc > > > while I < 11 > loop > if newly selected value = "ddl"+I.selectedindex.text then > "ddl"+I.selectedindex = 0 > end if > end loop > > in javascript there is a function eval() whose parameter is a string. > so results of that call eval("string_to_evaluate") gets executed or > interpreted as if you had type the string out directly. > > also, what would be the line of code to tell which dropdown the user > changed and cause the codebehind to trigger? what I was calling > "newly selected value" above > > thanks again for any help! > control by name" and you'll find some examples about it. However I'd so something like this. 1. Create an array Dim A(NumofControls-1) as Array 2. Create your handler code Private sub Combobox_SelectionChanged(Sender as object, e as EventArgs) handles DDL1.SelectionChanged, DDL2.SelectionChanged..... End Sub 3. Make your loop dim C as ComboBox dim ChangeBox as ComboBox = DirectCast(Sender, ComboBox) For ii as integer = 0 to NumofControls-1 C = DirectCast(A(ii), ComboBox) 'Make sure it is not the sender if not ChangeBox is C then 'Do your check here End if Next ii This code hasn't be checked but the idea is right. Also you'll see here how do know which object caused the event to fire with this code: dim ChangeBox as ComboBox = DirectCast(Sender, ComboBox) Hope is helps Chris That is fine for a round trip solution, however, couldn't this solution be
handled at the client. There is no reason to ask the server what to do, when the client has all of the data. <select id="box2" name="box2" onchange="cbochanged(this);"> <script language="jscript"> function cbochanged(cbo) { var oObject = document.all.item("Select"); for (i = 0; i < oObject.length; i++) { if (cbo.id != oObject.id) { oObject.selectedIndex=-1; } } } </script> Show quoteHide quote "Chris" <no@spam.com> wrote in message news:ekH$ugsGGHA.2000@TK2MSFTNGP15.phx.gbl... > simon wrote: >> hello, >> I have a form that has 10 dropdown lists in one section >> each of the dropdowns contain the same data >> >> what i'm looking to do is that when a user selects a value from one >> dropdown, change the value to null/nothing for any other dropdowns >> that may have had the same value as the one that was just selected. >> and have all the dropdowns use the same "selected index changed" code >> behind. >> >> so if ddl1 was changed, fire the code behind to sweep thru all the >> dropdowns and reset it if there was a match. >> >> was thinking of pseudo code for this would be something like.... >> assume all the dropdowns are named dd1,dd2,dd3,dd4,dd5,dd6,etc >> >> >> while I < 11 >> loop >> if newly selected value = "ddl"+I.selectedindex.text then >> "ddl"+I.selectedindex = 0 >> end if >> end loop >> >> in javascript there is a function eval() whose parameter is a string. >> so results of that call eval("string_to_evaluate") gets executed or >> interpreted as if you had type the string out directly. >> >> also, what would be the line of code to tell which dropdown the user >> changed and cause the codebehind to trigger? what I was calling >> "newly selected value" above >> >> thanks again for any help! >> > > Well you can do your "Eval" thing using reflection. Do a search on "get > control by name" and you'll find some examples about it. However I'd so > something like this. > > 1. Create an array > Dim A(NumofControls-1) as Array > > 2. Create your handler code > Private sub Combobox_SelectionChanged(Sender as object, e as EventArgs) > handles DDL1.SelectionChanged, DDL2.SelectionChanged..... > End Sub > > 3. Make your loop > dim C as ComboBox > dim ChangeBox as ComboBox = DirectCast(Sender, ComboBox) > For ii as integer = 0 to NumofControls-1 > C = DirectCast(A(ii), ComboBox) > 'Make sure it is not the sender > if not ChangeBox is C then > 'Do your check here > End if > Next ii > > This code hasn't be checked but the idea is right. Also you'll see here > how do know which object caused the event to fire with this code: > dim ChangeBox as ComboBox = DirectCast(Sender, ComboBox) > > Hope is helps > Chris AMDRIT wrote:
Show quoteHide quote > That is fine for a round trip solution, however, couldn't this solution be Ah, well it is helpful to know that you are using ASP.NET. I thought > handled at the client. There is no reason to ask the server what to do, > when the client has all of the data. > > <select id="box2" name="box2" onchange="cbochanged(this);"> > > <script language="jscript"> > > function cbochanged(cbo) > { > > var oObject = document.all.item("Select"); > > for (i = 0; i < oObject.length; i++) > { > if (cbo.id != oObject.id) > { > oObject.selectedIndex=-1; > } > } > > } > </script> > > > "Chris" <no@spam.com> wrote in message > news:ekH$ugsGGHA.2000@TK2MSFTNGP15.phx.gbl... > >>simon wrote: >> >>>hello, >>>I have a form that has 10 dropdown lists in one section >>>each of the dropdowns contain the same data >>> >>>what i'm looking to do is that when a user selects a value from one >>>dropdown, change the value to null/nothing for any other dropdowns >>>that may have had the same value as the one that was just selected. >>>and have all the dropdowns use the same "selected index changed" code >>>behind. >>> >>>so if ddl1 was changed, fire the code behind to sweep thru all the >>>dropdowns and reset it if there was a match. >>> >>>was thinking of pseudo code for this would be something like.... >>>assume all the dropdowns are named dd1,dd2,dd3,dd4,dd5,dd6,etc >>> >>> >>>while I < 11 >>>loop >>> if newly selected value = "ddl"+I.selectedindex.text then >>> "ddl"+I.selectedindex = 0 >>> end if >>>end loop >>> >>>in javascript there is a function eval() whose parameter is a string. >>>so results of that call eval("string_to_evaluate") gets executed or >>>interpreted as if you had type the string out directly. >>> >>>also, what would be the line of code to tell which dropdown the user >>>changed and cause the codebehind to trigger? what I was calling >>>"newly selected value" above >>> >>>thanks again for any help! >>> >> >>Well you can do your "Eval" thing using reflection. Do a search on "get >>control by name" and you'll find some examples about it. However I'd so >>something like this. >> >>1. Create an array >>Dim A(NumofControls-1) as Array >> >>2. Create your handler code >>Private sub Combobox_SelectionChanged(Sender as object, e as EventArgs) >>handles DDL1.SelectionChanged, DDL2.SelectionChanged..... >>End Sub >> >>3. Make your loop >>dim C as ComboBox >>dim ChangeBox as ComboBox = DirectCast(Sender, ComboBox) >>For ii as integer = 0 to NumofControls-1 >>C = DirectCast(A(ii), ComboBox) >>'Make sure it is not the sender >>if not ChangeBox is C then >>'Do your check here >>End if >>Next ii >> >>This code hasn't be checked but the idea is right. Also you'll see here >>how do know which object caused the event to fire with this code: >>dim ChangeBox as ComboBox = DirectCast(Sender, ComboBox) >> >>Hope is helps >>Chris > > > your javascript reference was just to illistrate an idea. That's what I get for being so winform bais. There is a document.getElementById("DDL1") This should work for you loop as you can just append the number to "DDL". My javascript knowledge is very limited though, so I can't help you beyond this. Chris i just asumed asp.net because simon made a reference to javascript in his
post. Your solution works either way. Show quoteHide quote "Chris" <no@spam.com> wrote in message news:eLcueFtGGHA.1180@TK2MSFTNGP09.phx.gbl... > AMDRIT wrote: >> That is fine for a round trip solution, however, couldn't this solution >> be handled at the client. There is no reason to ask the server what to >> do, when the client has all of the data. >> >> <select id="box2" name="box2" onchange="cbochanged(this);"> >> >> <script language="jscript"> >> >> function cbochanged(cbo) >> { >> >> var oObject = document.all.item("Select"); >> >> for (i = 0; i < oObject.length; i++) >> { >> if (cbo.id != oObject.id) >> { >> oObject.selectedIndex=-1; >> } >> } >> >> } >> </script> >> >> >> "Chris" <no@spam.com> wrote in message >> news:ekH$ugsGGHA.2000@TK2MSFTNGP15.phx.gbl... >> >>>simon wrote: >>> >>>>hello, >>>>I have a form that has 10 dropdown lists in one section >>>>each of the dropdowns contain the same data >>>> >>>>what i'm looking to do is that when a user selects a value from one >>>>dropdown, change the value to null/nothing for any other dropdowns >>>>that may have had the same value as the one that was just selected. >>>>and have all the dropdowns use the same "selected index changed" code >>>>behind. >>>> >>>>so if ddl1 was changed, fire the code behind to sweep thru all the >>>>dropdowns and reset it if there was a match. >>>> >>>>was thinking of pseudo code for this would be something like.... >>>>assume all the dropdowns are named dd1,dd2,dd3,dd4,dd5,dd6,etc >>>> >>>> >>>>while I < 11 >>>>loop >>>> if newly selected value = "ddl"+I.selectedindex.text then >>>> "ddl"+I.selectedindex = 0 >>>> end if >>>>end loop >>>> >>>>in javascript there is a function eval() whose parameter is a string. >>>>so results of that call eval("string_to_evaluate") gets executed or >>>>interpreted as if you had type the string out directly. >>>> >>>>also, what would be the line of code to tell which dropdown the user >>>>changed and cause the codebehind to trigger? what I was calling >>>>"newly selected value" above >>>> >>>>thanks again for any help! >>>> >>> >>>Well you can do your "Eval" thing using reflection. Do a search on "get >>>control by name" and you'll find some examples about it. However I'd so >>>something like this. >>> >>>1. Create an array >>>Dim A(NumofControls-1) as Array >>> >>>2. Create your handler code >>>Private sub Combobox_SelectionChanged(Sender as object, e as EventArgs) >>>handles DDL1.SelectionChanged, DDL2.SelectionChanged..... >>>End Sub >>> >>>3. Make your loop >>>dim C as ComboBox >>>dim ChangeBox as ComboBox = DirectCast(Sender, ComboBox) >>>For ii as integer = 0 to NumofControls-1 >>>C = DirectCast(A(ii), ComboBox) >>>'Make sure it is not the sender >>>if not ChangeBox is C then >>>'Do your check here >>>End if >>>Next ii >>> >>>This code hasn't be checked but the idea is right. Also you'll see here >>>how do know which object caused the event to fire with this code: >>>dim ChangeBox as ComboBox = DirectCast(Sender, ComboBox) >>> >>>Hope is helps >>>Chris >> >> >> > > Ah, well it is helpful to know that you are using ASP.NET. I thought your > javascript reference was just to illistrate an idea. That's what I get > for being so winform bais. > > There is a document.getElementById("DDL1") This should work for you loop > as you can just append the number to "DDL". > > My javascript knowledge is very limited though, so I can't help you beyond > this. > > Chris
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"simon" <m*@here.com> schrieb: \\\> I have a form that has 10 dropdown lists in one section > each of the dropdowns contain the same data > > what i'm looking to do is that when a user selects a value from one > dropdown, change the value to null/nothing for any other dropdowns > that may have had the same value as the one that was just selected. > and have all the dropdowns use the same "selected index changed" code > behind. > > so if ddl1 was changed, fire the code behind to sweep thru all the > dropdowns and reset it if there was a match. > > was thinking of pseudo code for this would be something like.... > assume all the dropdowns are named dd1,dd2,dd3,dd4,dd5,dd6,etc > > > while I < 11 > loop > if newly selected value = "ddl"+I.selectedindex.text then > "ddl"+I.selectedindex = 0 > end if > end loop Dim ComboBoxes() As ComboBox = _ { _ Me.ComboBox1, Me.ComboBox2, Me.ComboBox3 _ } ComboBoxes(i).SelectedIndex = 0 /// -- M S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://classicvb.org/petition/> thank you all for your replies. very much appreciate it....
i'm trying to stick with just using VB.net, just because i'm new to it and want to learn that route. have used other languages before, this is my new quest :) i'm going to try using both Chris and Herfrieds solutions (get a more well rounded understanding of the concepts and syntax) Herfried, what does the "Me." in "Me.ComboBox1" reference? Chris, when you define an array in vb.net, you do not need to specify the type of object it will hold? "Dim A(NumofControls-1) as Array" thanks again! On Mon, 16 Jan 2006 20:58:26 +0100, "Herfried K. Wagner [MVP]" Show quoteHide quote >> while I < 11 >> loop >> if newly selected value = "ddl"+I.selectedindex.text then >> "ddl"+I.selectedindex = 0 >> end if >> end loop > >\\\ >Dim ComboBoxes() As ComboBox = _ > { _ > Me.ComboBox1, Me.ComboBox2, Me.ComboBox3 _ > } >ComboBoxes(i).SelectedIndex = 0 >/// "simon" <m*@here.com> schrieb: It refers to the instance of the form. You can either type 'Me.ComboBox1' > i'm going to try using both Chris and Herfrieds solutions (get a more > well rounded understanding of the concepts and syntax) > > Herfried, what does the "Me." in "Me.ComboBox1" reference? or 'ComboBox1', which are semantically identical. > Chris, when you define an array in vb.net, you do not need to specify Use 'Dim A(...) As Object' instead.> the type of object it will hold? > > "Dim A(NumofControls-1) as Array" -- M S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://classicvb.org/petition/> simon wrote:
Show quoteHide quote > thank you all for your replies. very much appreciate it.... Me references the current object. If you are in a form, it references > i'm trying to stick with just using VB.net, just because i'm new to it > and want to learn that route. have used other languages before, this > is my new quest :) > > i'm going to try using both Chris and Herfrieds solutions (get a more > well rounded understanding of the concepts and syntax) > > Herfried, what does the "Me." in "Me.ComboBox1" reference? > > Chris, when you define an array in vb.net, you do not need to specify > the type of object it will hold? > > "Dim A(NumofControls-1) as Array" > > > thanks again! > > On Mon, 16 Jan 2006 20:58:26 +0100, "Herfried K. Wagner [MVP]" > >>>while I < 11 >>>loop >>> if newly selected value = "ddl"+I.selectedindex.text then >>> "ddl"+I.selectedindex = 0 >>> end if >>>end loop >> >>\\\ >>Dim ComboBoxes() As ComboBox = _ >> { _ >> Me.ComboBox1, Me.ComboBox2, Me.ComboBox3 _ >> } >>ComboBoxes(i).SelectedIndex = 0 >>/// > > the form. It is not needed, just there for readabilty. An array will accept an object type. That is why you see me using the directcast keyword to cast it out of object type back into a combobox. Chris thank you guys once again for the quick responses.
chris, in order to use the funtions that are part of the combobox object, i'd have to cast it out from object to combobox, correct? chris/herfried - use Object instead of Array, when creating the array of comboboxes? more accurate? "Use 'Dim A(...) As Object' instead." thanks again! On Mon, 16 Jan 2006 16:42:35 -0500, Chris <no@spam.com> wrote: Show quoteHide quote >Me references the current object. If you are in a form, it references >the form. It is not needed, just there for readabilty. > >An array will accept an object type. That is why you see me using the >directcast keyword to cast it out of object type back into a combobox. simon wrote:
Show quoteHide quote > thank you guys once again for the quick responses. Since you are new to programming let's leave it at you should cast it > chris, in order to use the funtions that are part of the combobox > object, i'd have to cast it out from object to combobox, correct? > chris/herfried - use Object instead of Array, when creating the array > of comboboxes? more accurate? > "Use 'Dim A(...) As Object' instead." > > thanks again! > > > On Mon, 16 Jan 2006 16:42:35 -0500, Chris <no@spam.com> wrote: > >>Me references the current object. If you are in a form, it references >>the form. It is not needed, just there for readabilty. >> >>An array will accept an object type. That is why you see me using the >>directcast keyword to cast it out of object type back into a combobox. out. It will help save you problems down the line. Also, put "option strict on" and "option explict on" at the top of your file. This will help save you errors. It also forces you to do the casting. Chris hello chris. thanks again for the tips. been programming for many
years, but brand new to vb/asp and .net i was assuming Object was the top level class that all classes inherit from. therefore you would need to cast your object to the appropriate class in order to have access to methods available at the more specific level. trying to get a hold of the .net framework concepts and don't really want to assume anything - especially if i assume it incorrectly :) I'll look up those file lines you recommended to learn more about them. thanks again for taking the time to reply. people in this group are much more resonsive than in the forums and its appreciated! On Mon, 16 Jan 2006 16:58:35 -0500, Chris <no@spam.com> wrote: Show quoteHide quote >Since you are new to programming let's leave it at you should cast it >out. It will help save you problems down the line. Also, put "option >strict on" and "option explict on" at the top of your file. This will >help save you errors. It also forces you to do the casting. 
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