Okay, just when I thought I was starting to understand stuff. In VB6...
Type MyDataType
Dim Value1 as double
Dim Value2 as double
End Type
Dim MyData1 as MyDataType
Dim MyData2 as MyDataType
MyData1=MyData2
'...Do stuff to MyData2, MyData1
When I did this in VB6, MyData1 and MyData2 were separate values (ie if I
changed values on one subsequently, the other remained unchanged). When the
code is converted to VB.NET, it changes Type to Structure. I read
documentation and it says structures are ValueTypes and not ReferenceTypes
like classes. So I expected the same behavior as in VB6. But in my converted
code, it appears that MyData1 is just a reference to MyData2 because
subsequent changes to one, change the other. What gives? And what is the
easiest way to create a cloned MyData1 instead of just a reference to
MyData2? I hope I don't have to go thru my VB6 code and set each value
inside the structure.
TIA,
Chuck 4 2507
In article <Ou************ **@TK2MSFTNGP12 .phx.gbl>, "Chuck Ritzke"
<CHUCK AT MYACTUARY DOT COM> says... Okay, just when I thought I was starting to understand stuff. In VB6...
Type MyDataType Dim Value1 as double Dim Value2 as double End Type
Dim MyData1 as MyDataType Dim MyData2 as MyDataType
MyData1=MyData2
'...Do stuff to MyData2, MyData1
When I did this in VB6, MyData1 and MyData2 were separate values (ie if I changed values on one subsequently, the other remained unchanged). When the code is converted to VB.NET, it changes Type to Structure. I read documentation and it says structures are ValueTypes and not ReferenceTypes like classes. So I expected the same behavior as in VB6. But in my converted code, it appears that MyData1 is just a reference to MyData2 because subsequent changes to one, change the other. What gives?
There must be something else wrong in your code. I was unable to
produce such behavior using this code:
Option Strict On
Option Explicit On
Structure MyDataType
Dim val1 As Double
Dim val2 As Double
End Structure
Module Module1
Sub Main()
Dim d1 As MyDataType
Dim d2 As MyDataType
d1.val1 = 11
d1.val2 = 22
d2 = d1
d1.val1 = 999
d1.val2 = 888
End Sub
End Module
--
Patrick Steele
Microsoft .NET MVP http://weblogs.asp.net/psteele
Thanks Patrick,
I looked further and realized that my problem happens because the value
inside the structure are arrays. Arrays inside the structure become
references to each other whereas primitive variables stay independent. It
sure would help to have a quick fix to handle this difference between VB6
and .NET.
So modifying your example...
Structure MyDataType
Dim val1() As Double
Dim val2 As Double
End Structure
Module Module1
Sub Main()
Dim d1 As MyDataType
Dim d2 As MyDataType
reDim d1.val1(1)
reDim d2.val1(1)
d1.val1(1) = 11
d2.val1(1) = 22
d1.val2=44
d2.val2=55
'AT THIS POINT BOTH ARRAYS AND VARIABLES INSIDE d1 and d2 ARE
INDEPENDENT
d2=d1
d2.val1(1) = 999
d2.val2=888
'NOW THE RESULT IS
'd1.val(1)=999 and d2.val(1)=999 and now reference each other
whereas...
'd1.val2=55 and d2.val2=88 are still independent
End Sub
End Module
"Patrick Steele [MVP]" <pa*****@mvps.o rg> wrote in message
news:MP******** *************** *@msnews.micros oft.com... In article <Ou************ **@TK2MSFTNGP12 .phx.gbl>, "Chuck Ritzke" <CHUCK AT MYACTUARY DOT COM> says... Okay, just when I thought I was starting to understand stuff. In VB6...
Type MyDataType Dim Value1 as double Dim Value2 as double End Type
Dim MyData1 as MyDataType Dim MyData2 as MyDataType
MyData1=MyData2
'...Do stuff to MyData2, MyData1
When I did this in VB6, MyData1 and MyData2 were separate values (ie if
I changed values on one subsequently, the other remained unchanged). When
the code is converted to VB.NET, it changes Type to Structure. I read documentation and it says structures are ValueTypes and not
ReferenceTypes like classes. So I expected the same behavior as in VB6. But in my
converted code, it appears that MyData1 is just a reference to MyData2 because subsequent changes to one, change the other. What gives?
There must be something else wrong in your code. I was unable to produce such behavior using this code:
Option Strict On Option Explicit On
Structure MyDataType Dim val1 As Double Dim val2 As Double End Structure
Module Module1
Sub Main() Dim d1 As MyDataType Dim d2 As MyDataType
d1.val1 = 11 d1.val2 = 22
d2 = d1
d1.val1 = 999 d1.val2 = 888 End Sub
End Module
-- Patrick Steele Microsoft .NET MVP http://weblogs.asp.net/psteele
It looks like I can write a "cloning" function for each UDT to handle
arrays...
Function CloneMyDataType (MyData as MyDataType)
Dim MyCopy as MyDataType
MyCopy=MyData
MyCopy.Val1=VB6 .CopyArray(MyDa ta.Val1)
'and repeat last line for each array in MyDataType
Return MyCopy
End Function
'Then instead of d2=d1
d2=CloneMyDataT ype(d1)
But do you have a quicker/better way? I have lots of UDT's each with lots of
arrays inside.
TIA,
Chuck
"Chuck Ritzke" <CHUCK AT MYACTUARY DOT COM> wrote in message
news:uk******** *****@tk2msftng p13.phx.gbl... Thanks Patrick,
I looked further and realized that my problem happens because the value inside the structure are arrays. Arrays inside the structure become references to each other whereas primitive variables stay independent. It sure would help to have a quick fix to handle this difference between VB6 and .NET.
So modifying your example...
Structure MyDataType Dim val1() As Double Dim val2 As Double End Structure
Module Module1
Sub Main() Dim d1 As MyDataType Dim d2 As MyDataType reDim d1.val1(1) reDim d2.val1(1)
d1.val1(1) = 11 d2.val1(1) = 22 d1.val2=44 d2.val2=55 'AT THIS POINT BOTH ARRAYS AND VARIABLES INSIDE d1 and d2 ARE INDEPENDENT
d2=d1
d2.val1(1) = 999 d2.val2=888 'NOW THE RESULT IS 'd1.val(1)=999 and d2.val(1)=999 and now reference each other whereas... 'd1.val2=55 and d2.val2=88 are still independent
End Sub
End Module
"Patrick Steele [MVP]" <pa*****@mvps.o rg> wrote in message news:MP******** *************** *@msnews.micros oft.com... In article <Ou************ **@TK2MSFTNGP12 .phx.gbl>, "Chuck Ritzke" <CHUCK AT MYACTUARY DOT COM> says... Okay, just when I thought I was starting to understand stuff. In
VB6... Type MyDataType Dim Value1 as double Dim Value2 as double End Type
Dim MyData1 as MyDataType Dim MyData2 as MyDataType
MyData1=MyData2
'...Do stuff to MyData2, MyData1
When I did this in VB6, MyData1 and MyData2 were separate values (ie
if I changed values on one subsequently, the other remained unchanged).
When the code is converted to VB.NET, it changes Type to Structure. I read documentation and it says structures are ValueTypes and not ReferenceTypes like classes. So I expected the same behavior as in VB6. But in my converted code, it appears that MyData1 is just a reference to MyData2 because subsequent changes to one, change the other. What gives?
There must be something else wrong in your code. I was unable to produce such behavior using this code:
Option Strict On Option Explicit On
Structure MyDataType Dim val1 As Double Dim val2 As Double End Structure
Module Module1
Sub Main() Dim d1 As MyDataType Dim d2 As MyDataType
d1.val1 = 11 d1.val2 = 22
d2 = d1
d1.val1 = 999 d1.val2 = 888 End Sub
End Module
-- Patrick Steele Microsoft .NET MVP http://weblogs.asp.net/psteele
In article <#k************ **@TK2MSFTNGP11 .phx.gbl>, "Chuck Ritzke"
<CHUCK AT MYACTUARY DOT COM> says... It looks like I can write a "cloning" function for each UDT to handle arrays...
In .NET you could implement the ICloneable interface and get basically
the same results.
But, in the end, you will have to copy the arrays manually when copying
the structs (types). This is known as a "deep copy". By default, you
get a "shallow copy" where only the reference to the array is copied --
thus making both structs point to a single array.
--
Patrick Steele
Microsoft .NET MVP http://weblogs.asp.net/psteele This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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