Genericize access to variables

David Knechtges

I googled this extensively yesterday and didn't come out with an answer: Is it possible to do some thing like this, and if so how? labela1.Text = "something"; labela2.Text = "something"; labela3.Text = "something"; Now what I want is a way to write that code as say: for (int i=1;i<4;i++) labelai.Text = "something"; so that the i in labelai above is replaced by 1, 2, 3 at runtime and the net result of the for loop is the same as what happens in the block above. Is there a way to do that? Thanks!

Ennis Ray Lynch Jr

Yes, however, you may not like it.

foreach(Control control in Controls){
if(control is Label){
((Label)control).Text = "Something";
}
}

Unfortunately this will set all labels. If you are in Windows forms you can use the Tag option to set a tag, or you can subclass your Label control to give it a type. The other option is, after Initialize component, place all Labels you care about looping through in a collection.

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Chris Trelawny Ross

Here's a refinement that will only touch all labels you care about:

foreach (Control control in Controls)
{
if (control is Label && label.Name.StartsWith("labelNamePrefixToModifyAsAGroup"))
{
((Label)control).Text = "Something";
}
}

Lost User

Hax..

Luc Pattyn

which can be reduced to

foreach (Control c in Controls) if (c.Name.StartsWith("labela")) c.Text = "Something";

as every Control has a Name and a Text property. :)

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Chris Trelawny Ross

Slaps self on head for missing that one. :doh:

realJSOP

Reference parameters are your friend:

private void SetLabelText(ref Label label, string text)
{
label.Text = text;
}

private void SomeFunction()
{
SetLabelText(ref label1, "something1");
SetLabelText(ref label2, "something2");
SetLabelText(ref label3, "something3");
}

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Ian Shlasko

No need for 'ref', unless you want to change what the label1, label2, and label3 variables point to.

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for (int i=1;1<4;i++){
this.Controls[string.Concat("labela", i.ToString())].Text = "something";
}

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Lost User

No-one with a LINQ version yet?

class Form1
{
IEnumerable<Control> summingLabels;

public Form1()
{
InitializeComponent();

summingLabels =
	from c in Controls.Cast().AsQueryable()
	where c.Name.StartsWith("sumLabel")
	select c;

// later on, when you need them
foreach(Control l in summingLabels)
	l.Text = l.Name;
}

}

Keep a pointer around to the controls that you found; no need to iterate them every time :)

I are Troll :suss:

Daniel Grunwald

The correct answer is: don't do that If you need multiple storage locations (variables) and access them by index, use an array. If you really have multiple variables (e.g. because they are generated by the VS forms designer), then you can still put those into an array:

Label[] labels = { labela1, labela2, labela3 };

PIEBALDconsult

Hear hear!

Paul Michalik

David Knechtges wrote:

Is there a way to do that?

No, at least if I understand what you want... However, why would you want to do that? What's wrong with:

Label[] labela = {
labela0,
labela1,
labela2,
labela3,
};
//...
for (int i=0;i<4;i++)
labela[i].Text = "something";

modified on Wednesday, September 1, 2010 5:55 PM

AspDotNetDev · modified on Wednesday, September 1, 2010 5:55 PM

This answer was already posted hours ago.

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Lukasz Nowakowski

You can also try reflection if you really really really really really really really really must do it this way and not using array/collection (depending on a situation).

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Alexander Voronin

Try to use this construction:

this.GetType().GetField("variablename")

This should work for c# but better try to avoid such kind of code. Other languages has different RTTI, for example in c/c++ this is impossible at all.

ExportedNorwegian

Not sure about the performance implications of FindControl.. But this one is pretty close to what you originally wrote

for (int i=1;i<4;i++)
(Controls.FindControl("labela" + i.ToString()) as Label).Text = "something";

BC3Tech

how about lambda? :)

foreach (Control l in Controls.Cast().Where(c => c.Name.StartsWith("sumLabel")))
l.Text = l.Name;

Dave Buhl

This is not exactly what you were asking for but is an alternative using binding. This may be overkill for what you are trying to do but it would be more elegant. Bind your labels as you create them to an object of a class that implements INotifyChanged then when you change the property of the object each label will be updated without having to work loops. http://stackoverflow.com/questions/639894[^] Dave

JaceTheAce

Array.ForEach(new Control[] { labela1, labela2, labela3 }, delegate(Control c) { c.Text = "something"; });