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Subject:
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listitem
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Posted By:
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alyeng2000
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Post Date:
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12/31/2003 4:33:58 PM
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i do the to scenarios but one only work
all i do is i populate the dropdownlist control with some rows retrieved from a Database table(only two fields returned),BUT
the problem seam to be with ListItem Class but why?
the follows are the two scenarios
scenario1:
dim listItem1 as new listitem
while datareader1.read
listItem1.value=datareader1("ID")
listItem1.Text=datareader1("Name")
DropDownList.items.add(listItem1)
loop
scenario2:
while datareader1.read
dim listItem1 as new listitem
listItem1.value=datareader1("ID")
listItem1.Text=datareader1("Name")
DropDownList.items.add(listItem1)
loop
but only scenario2 is the working one, do any one have an explaination
Ahmed Ali
Software Developer
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Reply By:
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planoie
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Reply Date:
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1/1/2004 8:52:30 AM
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When you have a declared object like your "listitem1" and you add this to another control, whether you add it to the other control's "controls" collection or an "items" collection the reference to the declared object doesn't go away. It doesn't "add and forget" the original object. If you take that same object and ".Add(...)" it to a different control, it leaves the first. If the first happens to be the same as the second, like in your scenario, it's still there, but it's not duplicated. I think this is due to the way the objects store references to other objects. You need to create a new instance of the control each time you need a new one.
One better way to do what you are doing is:
dim listItem1 as listitem
while datareader1.read
listItem1 = new listitem
listItem1.value=datareader1("ID")
listItem1.Text=datareader1("Name")
DropDownList.items.add(listItem1)
loop
Alternatively you could do this:
dim listItem1 as listitem
while datareader1.read
listItem1 = new listitem(datareader1("Name"), datareader1("ID"))
DropDownList.items.add(listItem1)
loop
Or:
while datareader1.read
DropDownList.items.add(new listitem(datareader1("Name"), datareader1("ID")))
loop
My recommendation is to drop the whole loop altogether and utilize the databinding capabilities of the control:
DropDownList.DataSource = datareader1
DropDownList.DataTextField = "Name"
DropDownList.DataValueField = "ID"
DropDownList.DataBind()
Peter
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Work smarter, not harder.
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Reply By:
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alyeng2000
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Reply Date:
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1/3/2004 9:13:14 AM
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txs Peter the last Databinding Sol. is the best
Ahmed Ali
Software Developer
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