Change case in ASP.NET webforms only on selected text

Question

I have a little problem with case change in ASP.NET webforms. What I have in my code, converts the whole entered text to uppercase, I want just a piece of the text to be converted. For example if I enter John Doe, the code bellow converts it to JOHN DOE. I need a result when I select only John to return JOHN Doe, this should work similar like a text editor. If anyone has a clue if this could be done in ASP.NET webforms I would be very grateful. Thanks in advance.

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="UpperCase" OnClick="Button1_Click" />

protected void Button1_Click(object sender, EventArgs e)
    {
        TextBox1.Style.Add("text-transform", "uppercase");
    }

Answer 1

Since you have a button click, and can (we assume) are going to run code, then this will work:

    protected void Button1_Click(object sender, EventArgs e)
    {
        if (TextBox1.Text != "")
        {
            string[] sParts = TextBox1.Text.Split(' ');
            sParts[0] = sParts[0].ToUpper();
            TextBox1.Text = string.Join(" ",sParts);
        }
    }

So, above takes the text to the first found space. Converts to upper case, and then shoves the results back into the text box.

FYI: The use of single quote and double quotes as per above is required for this to work.

Edit: convert selected text to upper case.

So, we want to allow the user to select some text in a box, and then convert to upper case.

So say we drop in a text box - lets go with multi-line, and alow the user to type in some text, and select some text, and then convert the selected text to upper case.

Thus this markup:

        <asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine" 
            Height="238px" Width="492px" ClientIDMode="Static"  >
        </asp:TextBox>
        <br />
        <br />
        <asp:Button ID="cmdUpper" runat="server" Text="Convert selected text to uppper"
            CssClass="btn"
            OnClientClick="MyUpper();return false" />

        <script>
            function MyUpper() {

                tBox = $('#TextBox1')
                selStart = tBox[0].selectionStart - 1
                selEnd = tBox[0].selectionEnd
                myUpper = tBox.val().substring(selStart, selEnd)
                myUpper = myUpper.toUpperCase()

                myResult = tBox.val().substring(0, selStart) + myUpper +
                    tBox.val().substring(selEnd)

                tBox.val(myResult)
            }
        </script>

So, we can now select some text, and hit the button, it will convert the text to upper case.

Eg this:

I of course assumed jQuery is available.