Problem with - Edit Item of Collections.Gen eric.List(Of SearchAreaListI tem)

[snesbit]

I have a structure called SearchAreaListI tem.

The structure has some properties.

The application implements this as a collection.gene ric.list(of SearchAreaListI tem)

I load the collection up item at a time stuffing values into the item then adding the item to the
collection.
Now here come the rub.

There is one property attached to SearchAreaListI tem, that I need to CHANGE so we can track whether the item has been accessed.

However when I try the following;
STEP 1: Dim SearchAreaList as new collection.gene ric.list(of SearchAreaListI tem)

STEP 2: Call function to load each item and add to collection

STEP 3: Try to set the Accessed property on Item X

SearchAreaList. Item(x).Accesse d = True

STEP 3 is not acceptable to Visual Studio and I get the design time error

Error 1 Expression is a value and therefore cannot be the target of an assignment.

Why can't I set a property of a structure through an index of a collection.gene ric.list(of SearchAreaListI tem)??

[Mattias Sjögren]

Why can't I set a property of a structure through an index of a collection.gene ric.list(of SearchAreaListI tem)??

Becuase a structure givs you a value type, and therefore the List
indexer returns a copy of the instance. Even if the compiler let you
do what you want, you would modify the temporary copy, not the one in
the list. The solution is to use a class (a reference type) instead.
Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Kerry Moorman]

snesbit,

In order to do what you want, SearchAreaListI tem needs to be a class, not a
structure.

Kerry Moorman
"snesbit" wrote:

I have a structure called SearchAreaListI tem.

The structure has some properties.

The application implements this as a collection.gene ric.list(of SearchAreaListI tem)

I load the collection up item at a time stuffing values into the item then adding the item to the
collection.
Now here come the rub.

There is one property attached to SearchAreaListI tem, that I need to CHANGE so we can track whether the item has been accessed.

However when I try the following;
STEP 1: Dim SearchAreaList as new collection.gene ric.list(of SearchAreaListI tem)

STEP 2: Call function to load each item and add to collection

STEP 3: Try to set the Accessed property on Item X

SearchAreaList. Item(x).Accesse d = True

STEP 3 is not acceptable to Visual Studio and I get the design time error

Error 1 Expression is a value and therefore cannot be the target of an assignment.

Why can't I set a property of a structure through an index of a collection.gene ric.list(of SearchAreaListI tem)??

[Cor Ligthert [MVP]]

Snesbit,

It sounds for me so crazy

A generic list of a value that is placed on the stack

Cor
"snesbit" <sn*****@portal tech.com> schreef in bericht news:Oe******** ******@TK2MSFTN GP09.phx.gbl...
I have a structure called SearchAreaListI tem.

The structure has some properties.

The application implements this as a collection.gene ric.list(of SearchAreaListI tem)

I load the collection up item at a time stuffing values into the item then adding the item to the
collection.
Now here come the rub.

There is one property attached to SearchAreaListI tem, that I need to CHANGE so we can track whether the item has been accessed.

However when I try the following;
STEP 1: Dim SearchAreaList as new collection.gene ric.list(of SearchAreaListI tem)

STEP 2: Call function to load each item and add to collection

STEP 3: Try to set the Accessed property on Item X

SearchAreaList. Item(x).Accesse d = True

STEP 3 is not acceptable to Visual Studio and I get the design time error

Error 1 Expression is a value and therefore cannot be the target of an assignment.

Why can't I set a property of a structure through an index of a collection.gene ric.list(of SearchAreaListI tem)??