Programming Forums > Application Development > C#

Robocop · May 3rd, 2008, 9:19 AM

I want to clear around 50 textbox's text after a click event is executed.

Do I have to set each textbox's text to empty by writing 50 lines of code? Or is there a better way?

Thanks

Jimbo · May 3rd, 2008, 12:27 PM

Technically, yes you do. You could possibly simplify it by keeping them all in a collection, and clearing them in a loop.

Robocop · May 3rd, 2008, 12:34 PM

I tried this, but I think it aint working because this is what it's doing:

"answer1.Text" = string.Empty;

which should be:

answer1.Text = string.Empty;

(Toggle Plain Text)

        ArrayList myList = new ArrayList();
        int n = 0;
        int max = 3;
        for (n = 1; n <= max; n++)
        {
            myList.Add("answer" + n + ".Text");
            object Answer = myList[0];
            Answer = string.Empty;
        }

Ps: how can this be posted as "c# code"?

Jimbo · May 3rd, 2008, 2:07 PM

Quote:

Originally Posted by Robocop

I tried this, but I think it aint working because this is what it's doing:

"answer1.Text" = string.Empty;

which should be:

answer1.Text = string.Empty;

(Toggle Plain Text)

        ArrayList myList = new ArrayList();
        int n = 0;
        int max = 3;
        for (n = 1; n <= max; n++)
        {
            myList.Add("answer" + n + ".Text");
            object Answer = myList[0];
            Answer = string.Empty;
        }

There's a couple problems with this code. First, you need to add the controls to the collection, not the Text properties. Also, you can't add them by giving a string with the control's name (unfortunately

). Also, you should use the length of the ArrayList instead of hardcoding a length, to make sure you get each one. Lastly, an optional recommendation, you could use a generic collection so that you don't have to use the Object type for each element. For exmaple:

 c# Syntax (Toggle Plain Text) 
List<TextBox> theBoxes = new List<TextBox>();
// when you create a new textbox, add it
TextBox foo = new TextBox();
theBoxes.Add(foo);
// later on, just go over each element in the arraylist and set each of their text properties
foreach (TextBox t in theBoxes) 
{
   t.Text = String.Empty;
}
// alternatively: 
//for(int i = 0; i < theBoxes.Count; i++)
//   theBoxes[i].Text = String.Empty;
List<TextBox> theBoxes = new List<TextBox>();
// when you create a new textbox, add it
TextBox foo = new TextBox();
theBoxes.Add(foo);
// later on, just go over each element in the arraylist and set each of their text properties
foreach (TextBox t in theBoxes) 
{
   t.Text = String.Empty;
}
// alternatively: 
//for(int i = 0; i < theBoxes.Count; i++)
//   theBoxes[i].Text = String.Empty;

Quote:

Ps: how can this be posted as "c# code"?

Instead of just using [code] you can often put [code=language] to get colored syntax. There are some anomalies as I recall, such as C++ being [code=cpp]. For C#, it's just [code=c#] though.

Robocop · May 3rd, 2008, 3:11 PM

Quote:

Originally Posted by Jimbo

There's a couple problems with this code. First, you need to add the controls to the collection, not the Text properties. Also, you can't add them by giving a string with the control's name (unfortunately

). Also, you should use the length of the ArrayList instead of hardcoding a length, to make sure you get each one. Lastly, an optional recommendation, you could use a generic collection so that you don't have to use the Object type for each element. For exmaple:

 c# Syntax (Toggle Plain Text) 
List<TextBox> theBoxes = new List<TextBox>();
// when you create a new textbox, add it
TextBox foo = new TextBox();
theBoxes.Add(foo);
// later on, just go over each element in the arraylist and set each of their text properties
foreach (TextBox t in theBoxes) 
{
   t.Text = String.Empty;
}
// alternatively: 
//for(int i = 0; i < theBoxes.Count; i++)
//   theBoxes[i].Text = String.Empty;
List<TextBox> theBoxes = new List<TextBox>();
// when you create a new textbox, add it
TextBox foo = new TextBox();
theBoxes.Add(foo);
// later on, just go over each element in the arraylist and set each of their text properties
foreach (TextBox t in theBoxes) 
{
   t.Text = String.Empty;
}
// alternatively: 
//for(int i = 0; i < theBoxes.Count; i++)
//   theBoxes[i].Text = String.Empty;

Instead of just using [code] you can often put [code=language] to get colored syntax. There are some anomalies as I recall, such as C++ being [code=cpp]. For C#, it's just [code=c#] though.

From what I can see, the main difference between the ArrayList and List is that with the List you need to specify a class, and with the ArrayList you don't specify a type, am I right?

Also, maybe I didn't explain myself well, but I was looking for an alternative to having a line of code for each textbox, eg:

theBoxes.Add(answer1);
theBoxes.Add(answer2);
theBoxes.Add(answer3);

and so on...

Thanks alot for the help!

Jimbo · May 3rd, 2008, 3:30 PM

What about trying the following approach?

 c# Syntax (Toggle Plain Text) 
class foobar
{
	private List<TextBox> theBoxes;
 
	private TextBox MakeNewTextbox()
	{
		TextBox foo = new TextBox();
		theBoxes.Add(foo);
		return foo;
	}
}
class foobar
{
	private List<TextBox> theBoxes;

	private TextBox MakeNewTextbox()
	{
		TextBox foo = new TextBox();
		theBoxes.Add(foo);
		return foo;
	}
}

Then, instead of doing answer1 = new Textbox();, you would do answer1 = MakeNewTextbox();. Then you can set any properties for answer1, and clear all of the textboxes with a loop as discussed above.

As to List<> vs. ArrayList, I prefer the former because when you know the type of objects it contains. List[i] will always return a TextBox (or whatever type was declared), and you don't have to downcast it from Object. ArrayList will hold anything (which can be useful) but if you know the type of each object, you have to cast it before using it. Since in this case, you need to modify each TextBox's Text property, you'll be wanting to pull out variables of type TextBox; it's easier to use the List<> way of doing it.

kruptof · May 3rd, 2008, 4:11 PM

May I ask what are you doing with 50 textboxes?

lectricpharaoh · May 3rd, 2008, 4:33 PM

Another benefit to using generics is that it provides greater type safety. If you've got a plain ArrayList to hold your shit, it's only a matter of time until some idiot comes along and puts the wrong type in it. If you're using a generic type, then this will yield a compile-time error, and you can easily fix it.

May 3rd, 2008, 9:19 AM	#1
Robocop Programmer Join Date: Sep 2004 Posts: 42 Rep Power: 0	Clearing multiple textbox's text I want to clear around 50 textbox's text after a click event is executed. Do I have to set each textbox's text to empty by writing 50 lines of code? Or is there a better way? Thanks

May 3rd, 2008, 12:27 PM	#2
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 747 Rep Power: 3	Re: Clearing multiple textbox's text Technically, yes you do. You could possibly simplify it by keeping them all in a collection, and clearing them in a loop. __________________ <insert disclaimer here> <insert shameless plug for Visual Studio here>

May 3rd, 2008, 12:34 PM	#3
Robocop Programmer Join Date: Sep 2004 Posts: 42 Rep Power: 0	Re: Clearing multiple textbox's text I tried this, but I think it aint working because this is what it's doing: "answer1.Text" = string.Empty; which should be: answer1.Text = string.Empty; (Toggle Plain Text) ArrayList myList = new ArrayList(); int n = 0; int max = 3; for (n = 1; n <= max; n++) { myList.Add("answer" + n + ".Text"); object Answer = myList[0]; Answer = string.Empty; } ArrayList myList = new ArrayList(); int n = 0; int max = 3; for (n = 1; n <= max; n++) { myList.Add("answer" + n + ".Text"); object Answer = myList[0]; Answer = string.Empty; } Ps: how can this be posted as "c# code"?

May 3rd, 2008, 3:30 PM	#6
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 747 Rep Power: 3	Re: Clearing multiple textbox's text What about trying the following approach? c# Syntax (Toggle Plain Text) class foobar { private List<TextBox> theBoxes; private TextBox MakeNewTextbox() { TextBox foo = new TextBox(); theBoxes.Add(foo); return foo; } } class foobar { private List<TextBox> theBoxes; private TextBox MakeNewTextbox() { TextBox foo = new TextBox(); theBoxes.Add(foo); return foo; } } Then, instead of doing `answer1 = new Textbox();`, you would do `answer1 = MakeNewTextbox();`. Then you can set any properties for answer1, and clear all of the textboxes with a loop as discussed above. As to List<> vs. ArrayList, I prefer the former because when you know the type of objects it contains. List[i] will always return a TextBox (or whatever type was declared), and you don't have to downcast it from Object. ArrayList will hold anything (which can be useful) but if you know the type of each object, you have to cast it before using it. Since in this case, you need to modify each TextBox's Text property, you'll be wanting to pull out variables of type TextBox; it's easier to use the List<> way of doing it. __________________ <insert disclaimer here> <insert shameless plug for Visual Studio here>

May 3rd, 2008, 4:33 PM	#8
lectricpharaoh Caffeinated Neural Net Join Date: Jun 2005 Location: Dry west coast of Canada Posts: 925 Rep Power: 4	Re: Clearing multiple textbox's text Another benefit to using generics is that it provides greater type safety. If you've got a plain `ArrayList` to hold your shit, it's only a matter of time until some idiot comes along and puts the wrong type in it. If you're using a generic type, then this will yield a compile-time error, and you can easily fix it. __________________ A man's knowledge is like an expanding sphere, the surface corresponding to the boundary between the known and the unknown. As the sphere grows, so does its surface; the more a man learns, the more he realizes how much he does not know. Hence, the most ignorant man thinks he knows it all. - L. Sprague de Camp

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Programming Forums > Application Development > C#

Clearing multiple textbox's text