Vb net references not updating

Vb net references not updating

Apologies for long delay in responding to your comment. I never really gave it much thought, so thanks for making me think about this issue. String Builder VB$t_ref$L0) IL_0000: nop IL_0001: newobj instance void [mscorlib]System. String Builder::.ctor() IL_0006: stloc.0 IL_0007: ldloc.0 IL_0008: stloc.2 IL_0009: ldloc.2 IL_000a: ldstr "foo" IL_000f: callvirt instance class [mscorlib]System. It is like a pointer in reverse, it un-points to the actual data. What is the use case for such a programming construct? depending on the size of the block as well of course. User ID="0" ...so on In the later example there are even performance benefit over the first example because in the first example Im fetching the user every time I access a user property and in the WITH-case I only fetch the user one time. NET, it compiles to exactly the same code as fully-qualifying the object name, so there is no performance penalty for this sugar. Append("zap") End With Dim sb2 As New String Builder sb2. For obvious reasons, I won't provide an example of such messy code I would be suspicious of code that uses a lot this keyword: if it is used to make easier to set lots of instance variables or properties I think this may indicate that your classes are too large ( Large Class smell ). Don't use it if it just happens to be some messages sent to the same object. Not only is its use easier on the eyes, but for repeated access to properties of an object, it's likely to be faster, as the object is fetched through the method chain only once, and not once for every property. Append("zap") End Sub End Class .method public instance void Foo() cil managed { // Code size 91 (0x5b) .maxstack 2 .locals init ([0] class [mscorlib]System. The WITH statement establishes a local, temporary, invariant pointer to the object (not a local copy of the object) and within the scope of the WITH statement will reliably refer to the same object all the way through regardless of what side effects the code might have. Avoid doing anything else with "With" If you write a With block that spans 50-100 lines and involves lots of other variables it can make it REALLY difficult to remember what was declared at the top of the block. A summary of the pattern: use it when it makes sense to group the messages sent to the object. If during the execution of the WITH statement, the original variable reference is changed, the object referenced by the WITH does not change. @yu_ominae: It makes it harder if there are names in common - and harder in general to know which name is associated with which object. Updating a local copy versus the original is not what I would call a "subtle" distinction. WITH Block = "code broken" in many possible circumstances. It's probably fine if used to abbreviate syntax whilst staying within the structure of the same object... String Builder:: Append(string) IL_0014: pop IL_0015: ldloc.2 IL_0016: ldstr "bar" IL_001b: callvirt instance class [mscorlib]System. The most likely situation is where you may be traversing a structure such as a network of objects whose interconnections my be implicitly changed by setting properties. End With" blocks referring to different objects within each other.

At work, I'm frequently working on projects where numerous properties of certain objects have to be set during their construction or early during their lifetime.

For the sake of convenience and readability, I often use the User Handler.

It is certainly a trap for the unwary, but the way WITH block works, as implemented, is the most robust approach imho. It is a pattern in Kent Beck's Smalltalk Best Practice Patterns book.

I don't think it is right to say "code broken". The 'with' is basically the 'cascade' from Smalltalk.

And I just took this as an example so dont complain over a class with many keywords, another example could be like: WITH Refund Dialog. If you're doing this at other times in the object's life cycle, that sounds like a code smell to me, suggesting that there should probably be one combined operation which does all the appropriate things. IF you reformat the code by ONLY dropping the With and End With, and adding line continuation characters at the end of the first three lines...

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I can get the performance gain without using with, like this: But I would go for the WITH statement instead, it looks cleaner. I ascertained this by compiling, then disassembling, the following VB . Text Public Class Class1 Public Sub Foo() Dim sb As New String Builder With sb . If you use it to replace long chains of calls like this: User Handler. I do agree with other replies that you ought to avoid nested use of C# 3.0 has it for object initialization, where it's frequently useful.

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