convert string to a class data type

[nakhatib]

for example:

DIM A AS STRING="textbox1"

 

dim c as control= ' here i want to convert the string in the A variable to a datatype

 

can i do that.

This is a general question. The datatype i want to convert to, is not a standard datatype, it is a class data type.

 

Thank you

[AlexCode]

To convert datatypes you have to use CType.

Dim A As String = "123"
Dim B As Integer = CType(A, Integer)

Alex :D

[nakhatib]

I already tried ctype but it does not work

[PlausiblyDamp]

Could you give a bit more information? What is the datatype you want to convert the string to and what relation is the string to this datatype?

[nakhatib]

the example

 

this is what i want to do exactly:

 

dim t as textbox

dim s as string="textbox1"

t=s 'here i want to convert the string "s" to a textbox type

[PlausiblyDamp]

If the control already exists on the form then you could find it through a loop

Dim s As String = "TextBox1"
Dim t As TextBox

Dim c As Control
For Each c In Me.Controls
   If c.Name = s Then
       t = c
       Exit For
   End If
Next

 

There may be a better way but that should do the trick.

[nakhatib]

i think no one in the world knows the answer (""""""""""""""""""""""""""" UNFORTUNATELY """"""""""""""""""""""""""""""""""""")

:( ::mad: :-\

:confused:

[PlausiblyDamp]

Still not sure what you mean. Given a string TextBox1 do you want to find an existing textbox or create a new textbox?

[nakhatib]

The string represent an existing textbox named textbox1.

I want the methodology used to convert strings to class types. the ctype did not work, the type.gettype did not work, the gettype did not work.

I do not want to use late binding, this means that i do not want to define the textbox variable as object.

What i want is to define a variable of type textbox like this: dim a as textbox. and then i want this variable(a) to represent an existing textbox on the form that its name stored in a string variable.

So i mean that the string content must be converted to a textbox type(textbox1) which is already exist and then make my variable a represent this existing textbox "textbox1"

I hope it is clear now.

[PlausiblyDamp]

did you try the code I posted earlier?

Dim s As String = "TextBox1"
Dim t As TextBox

Dim c As Control
For Each c In Me.Controls
   If c.Name = s Then
       t = c
       Exit For
   End If
Next

[nakhatib]

i know this methodology. i do not want to use it, because i need performance (looping through the controls collection that contains 300 controls in my case). i need a direct conversion mechanism to optimize performance.

[splice]

It's Not possible to do that cast! You could however create a hashtable with the key being the objects name and the value is the Control object. That's about as fast as you are going to get....

 

So, when you want to access a control it would go something like this:

 

Dim c As Control = DirectCast(ctlTable("text name"), Control)

 

Keep in mind that looping over 300 objects in an array *should not * lag your application.

Edited January 15, 2004 by splice

[nakhatib]

it should be made the way i told you about. i will try to do more searches in the Reflection library(i think the answer is there). If i find the solution i will submit it.

[beekde]

From http://drgui.coldrooster.com/DrGUIdotNet/4/drguinet4code.htm

 

// s should include the full assembly to the class

string s = "TextBox1";

TextBox t;

 

Type stype = Type.GetType(s);

t = System.Activator.CreateInstance(stype);

[nakhatib]

i already mentioned that type.gettype did not work. the example you submit is not working. it is working only with classes you create, but it will not work with .net classes like textboxes and other controls.

[beekde]

Sorry I misunderstood. I believe splice had the most elegant solution to your problem. To expand upon it here is a sample. I agree you should be able to do it your way. Let us know if you find out how.

 

TextBox TextBox1 = new TextBox();

TextBox1.Text = "Hello World";

System.Collections.Hashtable map = new Hashtable();

map.Add("TextBox1", TextBox1);

 

string s = "TextBox1";

TextBox t = (TextBox) map;

Console.WriteLine(t.Text);

[splice]

This might be a bit more simplified.

 

Private Function FindControl(ByVal ctl As Control.ControlCollection, ByVal name As String) As Control
       Dim c As Windows.Forms.Control
       Dim t As Windows.Forms.Control

       For Each c In ctl
           If (name = c.Name()) Then
               Return c
           ElseIf (c.Controls().Count() > 0) Then
               t = FindControl(c.Controls(), name)
               If (Not t Is Nothing) Then Return t
           End If
       Next c
       Return Nothing
   End Function

 

Call example (in Form class):

 

 Dim c As Control = FindControl(Me.Controls(), "btnName")

 

On a form with 60+ controls it took an average of 0.055ms to find the control on a P3-700 system.... lag.... I think not. :P

Edited January 26, 2004 by splice