Substring not working as expected

Question

This seems like a fairly straightforward problem but I keep getting the same exception and I have no idea why.

I can only assume that it has something to do with a misunderstanding of how substring works in VB.NET.

The following code, keeps throwing a ArgumentOutOfRange exception:

    <%=Html.Encode(IIf(item.description.Length > 150, item.description.Substring(0, 150), item.description))%>

Now what should happen here is, if item.description is over a 150 characters output the first 150 otherwise output the entire string. Problem is it keeps trying to get the sub-string regardless of the length of the result of the if statement.

Any help would be greatly appreciated.

Check this: http://stackoverflow.com/questions/28377/iif-vs-if — Kapil Khandelwal, Dec 01 '12 at 20:30

score 3 · Answer 1 · answered Dec 01 '12 at 20:18

3

Use the If(expression,truepart,falsepart) operator instead: the IIF operator attempts to evaluate both the true and false parts whereas the If operator only attempts to evaluate the relevant part.

answered Dec 01 '12 at 20:18

Andrew Morton

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score 2 · Accepted Answer · answered Dec 01 '12 at 20:18

When you use IIF you evaluate all the expressions - the true as well as the false "branches".

This means that for strings that are under 150 characters long, you still call item.description.Substring(0, 150), causing the error.

Perhaps have an item.ShortDescription which only ever return the first 150 characters, using a normal IF/THEN.

score 0 · Answer 3 · edited May 23 '17 at 11:48

0

Try using:

Check this:IIf() vs. If

If(item.description.Length > 150) Then
  item.description.Substring(0, 150) 
Else 
  item.description
End If

OR,

If(item.description.Length > 150, item.description.Substring(0, 150), item.description)

edited May 23 '17 at 11:48

Community

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answered Dec 01 '12 at 20:21

Kapil Khandelwal

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Substring not working as expected

3 Answers3