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How to position the cursor inside a string?

Posted on 2008-06-12
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Last Modified: 2010-10-27
Hi Experts!
How can I set the position of the cursor to a precise point on a string?
For example: Between two html tags (<a href="blah">*</a>) I need the cursor where the asterisk is. Is there a way to get that to work?
Thanks in advance.
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Question by:jorgemgonzalez
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18 Comments
 
LVL 48

Expert Comment

by:jpaulino
Comment Utility
If you're using that on WinForms you can use SelectionStart and SelectionLenght. You just need to find the position you want.

Look to this example how to use that:
http://msdn.microsoft.com/en-us/library/system.windows.forms.textboxbase.selectionstart(VS.85).aspx
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Author Comment

by:jorgemgonzalez
Comment Utility
Thanks jpaulino for your fast reply.

Let me clarify for you.
What I need is to make the I beam to appear in a given part of a text line, let's say that we have a string like this"
strAddr = "<a href=""""></a>"
Then on a click of a button the string is passed to a textbox
TextBox1.SelectedText = strAddr

Now, in TextBox1 I need to have the I beam between ">" and "<" so the user can input text without having to position the I beam.
 The result should look like this: <a href="""">cursor</a> (Where "cursor" is the I beam)
Can that be done programmaticaly?
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LVL 48

Expert Comment

by:jpaulino
Comment Utility
You can look (using IndexOf) the position of the tag "</a>" and then position the cursor there.

Something like:
        Dim str As String = Me.TextBox1.Text

        Me.TextBox1.SelectionLength = 0

        Me.TextBox1.SelectionStart = str.IndexOf("</a>")

        Me.TextBox1.Select()

Open in new window

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Author Comment

by:jorgemgonzalez
Comment Utility
It gives me an error: InvalidArgument=Value of '-1' is not valid for 'SelectionStart'. Parameter name: SelectionStart
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LVL 48

Expert Comment

by:jpaulino
Comment Utility
-1 is because it couldn't find the expression that you have entered. Check if you really have that tag in the text or if it has spaces.
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Author Comment

by:jorgemgonzalez
Comment Utility
Yup, the tag is there, it's passed to the text box by another form.

However, the length of the string may vary, on the other hand, I wonder what would happen if the tag is inserted again some text after.

This is what I have there:


Private Sub cmdOk_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdOk.Click

        Dim Doc As frmDoc

        Doc = frmMain.ActiveMdiChild

        If Me.CheckBox1.Checked = True And Me.RadioButton1.Checked = True Then

            strAddr = "<a href=" & """" & Me.TextBox1.Text & """" & ">" & Me.TextBox3.Text & "</a>"

        ElseIf Me.CheckBox2.Checked = True And Me.RadioButton1.Checked = True Then

            strAddr = "<a href=" & """" & Me.TextBox1.Text & """" & ">" & Me.lblImg.Text & "</a>"

        ElseIf Me.CheckBox1.Checked = True And Me.RadioButton2.Checked = True Then

            strAddr = "<a href=" & """" & "mailto:" & Me.TextBox1.Text & "?subject= " & Me.TextBox2.Text & """" & ">" & Me.TextBox3.Text & "</a>"

        ElseIf Me.CheckBox2.Checked = True And Me.RadioButton2.Checked = True Then

            strAddr = "<a href=" & """" & "mailto:" & Me.TextBox1.Text & "?subject= " & Me.TextBox2.Text & """" & ">" & Me.lblImg.Text & "</a>"

        End If

        Doc.TextBox1.SelectedText = strAddr

        Me.Close()

    End Sub

Open in new window

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LVL 48

Expert Comment

by:jpaulino
Comment Utility

And where do you use the SelectionStart ?

>> I wonder what would happen if the tag is inserted again some text after.
If will find the first that it found and place the cursor there.

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Author Comment

by:jorgemgonzalez
Comment Utility
I remember a program I tried long ago, called "Edit+", you could write your own "snippets" and you could place the cursor in that snippet by typing ^!, and when you imported your snippet the cursor appeared where the "^!" was. I which I know how they did it! :)
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Author Comment

by:jorgemgonzalez
Comment Utility
No, I gave you what I had originally so you can analize the string
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Author Comment

by:jorgemgonzalez
Comment Utility
That's what I was thinking, but the thing is that the tag might be repeated several times.

There mught be a trick tough.
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LVL 48

Expert Comment

by:jpaulino
Comment Utility
You open a MDI chield and add the text using the above code. Then you try to place the cursor where ? After this line ?
Doc.TextBox1.SelectedText = strAddr

Try this way:
Doc.TextBox1.SelectedText = strAddr
Doc.TextBox1.SelectionLength = 0
Doc.TextBox1.SelectionStart = strAddr.IndexOf("</a>")
Me.Close()

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Author Comment

by:jorgemgonzalez
Comment Utility
It works my friend, but only is there's no other text in the textbox, if there is it places the cursor somewhere else, that's exactly my dilemma.

I really appreciate your effort.
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LVL 48

Expert Comment

by:jpaulino
Comment Utility
>> only is there's no other text in the textbox, if there is it places the cursor somewhere else, that's exactly my dilemma.

But should place before the tag. If you have <a href="">fdsfdfs1</a> it should place after the 1 and before the tag.

Maybe I'm understanding wrongly! Can you give one or two examples of what you have an what you need (not the code but the text you have)
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Author Comment

by:jorgemgonzalez
Comment Utility
What i'm doing is a simple html editor, as such, before an anchor tag there goes a lot of text. Once that text is there, by setting the selection length at 0, the cursor goes to the place equivalent to the lenght of the tag string before the </a> (strAddr.IndexOf("</a>"))

Now, if the textbox in the parent form is empty (selection lenght = 0) then it works like a charm.

What I need is a way to get the cursor appear before </.a> anytime the tag is inserted regardless of the amount of text in the editor (textbox) if there's any.

Thanks a lot for your patience.
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LVL 48

Accepted Solution

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jpaulino earned 500 total points
Comment Utility
And this way:

Doc.TextBox1.SelectionLength = 0
Doc.TextBox1.SelectionStart = Doc.TextBox1.Text.IndexOf("</a>")
Me.Close()

I really think this is an easy thing but I'm missing something. Do you want that I upload an example or can you upload your projetc (www.ee-stuff.com) ? you can delete the unecessary stuff if you want.
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Author Comment

by:jorgemgonzalez
Comment Utility
With this other approach:
Doc.TextBox1.SelectionLength = 0
Doc.TextBox1.SelectionStart = Doc.TextBox1.Text.IndexOf("</a>")
Me.Close()
it works fine, the problem I have still is that if the user needs to add another link tag after some other text then the selection will be at the first </a>
What can be done?
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Author Comment

by:jorgemgonzalez
Comment Utility
Well, I figured out that using:
Dim StartPos As Integer = Doc.TextBox1.SelectionStart
Doc.TextBox1.SelectedText = strAddr
        Doc.TextBox1.SelectionLength = StartPos
        Doc.TextBox1.SelectionStart = StartPos + strAddr.IndexOf("</a>")
        Doc.TextBox1.Select()
        Doc.TextBox1.SelectionLength = 0
it works on every occasion, I just don't know how orthodox or appropriate the method is, but it's working!

Thanks a million jpaulino for pointing me in the right direction.
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Author Closing Comment

by:jorgemgonzalez
Comment Utility
Thanks for your patience
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