Indirection Functionality

[Chris Mitroka]

I'm writing a C# class and need to do something known to me in Cache
(another language) as indirection. Not sure if the functionality exists in
C#, but could really use some help here. Basically, pretend a method takes
in two string variables: field (and we'll say the value is Name) and
fieldvalue (and we'll say the value is Chris). This is within a public
class having a field of Name. I need that variable to now be set to Chris.
Any ideas how I can accompilsh this without a switch or if/else?

[Rudy Velthuis]

Chris Mitroka wrote:

I'm writing a C# class and need to do something known to me in Cache
(another language) as indirection. Not sure if the functionality
exists in C#, but could really use some help here. Basically,
pretend a method takes in two string variables: field (and we'll say
the value is Name) and fieldvalue (and we'll say the value is Chris).
This is within a public class having a field of Name. I need that
variable to now be set to Chris. Any ideas how I can accompilsh this
without a switch or if/else?

Are you perhaps talking about reference parameters? Hmmm...

public void SetField(ref string field, string fieldvalue)
{
field = fieldvalue;
}

And it is called like:

SetField(ref FirstName, "Chris");
SetField(ref LastName, "Mitroka");

Of course, the types must match, but you could overload to make it work
for several types.

But I am not entirely sure that is what you are talking about.
--
Rudy Velthuis http://rvelthuis.de

"I'm so poor I can't even pay attention." -- Unknown

[Family Tree Mike]

Looks like I just attempted an answer to your second post.

"Chris Mitroka" <cm******@comcast.netwrote in message
news:OZ**************@TK2MSFTNGP03.phx.gbl...

I'm writing a C# class and need to do something known to me in Cache
(another language) as indirection. Not sure if the functionality exists
in C#, but could really use some help here. Basically, pretend a method
takes in two string variables: field (and we'll say the value is Name) and
fieldvalue (and we'll say the value is Chris). This is within a public
class having a field of Name. I need that variable to now be set to
Chris. Any ideas how I can accompilsh this without a switch or if/else?

[Chris Mitroka]

Just a heads up - I've never used 'Newsgroups', so I'm not sure if my
responses are working correctly or going to the right people.

I think I did a bad job explaining what I'm trying to accomplish. Here's a
quick example with some code:
public partial class Form1 : Form
{
private string FName;
private string LName;
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
SetIt("FName", "Chris");
}
private void SetIt(string WhatToSet, string SetItTo)
{
//Code would set the global var FName (or LName) to whatever
SetItTo is
}
}
So if anyone knows code that could make this work (IE: Fill in the SetIt
method), it would be appreciated.

Now I think the reflection thing was heading down the right path, but
couldn't get the set to work. Here some code of what I tried:
Type myTypeA = typeof(ID3v2);
FieldInfo myFieldInfo = myTypeA.GetField("Album");
myFieldInfo.SetValue("Album",CodeValue);

[Peter Duniho]

On Sat, 25 Oct 2008 20:21:04 -0700, Chris Mitroka <cm******@comcast.net>
wrote:

[...]
So if anyone knows code that could make this work (IE: Fill in the SetIt
method), it would be appreciated.

Now I think the reflection thing was heading down the right path, but
couldn't get the set to work. Here some code of what I tried:
Type myTypeA = typeof(ID3v2);
FieldInfo myFieldInfo = myTypeA.GetField("Album");
myFieldInfo.SetValue("Album",CodeValue);

Yes, reflection would be one way to approach the problem.

However, IMHO it's not a great way to go. It's slow, and it's not very
maintainable. It seems to me that if you want to get and/or set values
based on a string rather than a compiled identifier, you should store your
values in a Dictionary.

That's assuming, of course, that specifying the value to set by a string
is in fact the best approach in the first place; in the code you posted,
it's not clear at all why you wouldn't just use the variable itself (or,
frankly, why you're calling a separate method at all...a different example
where it's more clear _why_ you want to do this might help). It's
possible that what you really want is something like this:

SetIt(out FName, "Chris");

with:

void SetIt(ref string WhatToSet, string SetItTo)
{
WhatToSet = SetItTo;
}

If you want to be able to access the value by string _and_ a compiled
identifier, you could always add a property that goes through the
Dictionary to set and get the value.

By the way, I wouldn't call "FName" and "LName" global variables. They
are member fields of the class Form1. C# doesn't really have the concept
of global variables at all.

Pete

[Peter Duniho]

On Sat, 25 Oct 2008 21:50:25 -0700, Peter Duniho
<Np*********@nnowslpianmk.comwrote:

void SetIt(ref string WhatToSet, string SetItTo)

This, of course, should be:

void SetIt(out string WhatToSet, string SetItTo)

Sorry.

[Chris Mitroka]

I REALLY appreciate all the help. Using reflection, I was able to
accomplish my goal. Again, thank you all for your assistance.

[Ignacio Machin ( .NET/ C# MVP )]

On Oct 25, 5:29 pm, "Rudy Velthuis" <[e-mail]:

Chris Mitroka wrote:

I'm writing a C# class and need to do something known to me in Cache
(another language) as indirection. Not sure if the functionality
exists in C#, but could really use some help here. Basically,
pretend a method takes in two string variables: field (and we'll say
the value is Name) and fieldvalue (and we'll say the value is Chris).
This is within a public class having a field of Name. I need that
variable to now be set to Chris. Any ideas how I can accompilsh this
without a switch or if/else?

Are you perhaps talking about reference parameters? Hmmm...

public void SetField(ref string field, string fieldvalue)
{
field = fieldvalue;
}

And it is called like:

SetField(ref FirstName, "Chris");
SetField(ref LastName, "Mitroka");

Of course, the types must match, but you could overload to make it work
for several types.

But I am not entirely sure that is what you are talking about.
--
Rudy Velthuis http://rvelthuis.de

"I'm so poor I can't even pay attention." -- Unknown

Hi,

I do not see how the above code solve the problem. I think you did not
understand the post. The method receive a parameter that indicate
which property of the class will be set.