Changing HTML elements with Webbrowser - vb.net

Question

I have a question, how to change HTML input value?
<select name="sys_lenght" aria-controls="systable" class>
<option value="20">Value 1</option>
<option value="40">Value 2</option>
<option value="80">Value 3</option>
</select>
I used this code
For Each Elementz In WebBrowser1.Document.GetElementsByTagName("select")
If Elementz.Name = "sys_lenght" Then
Elementz.setAttribute("value", "80")
End If
Next
But it doesn't change the input value, only the text "Value 3".
How can I solve this problem? Thanks

Answer 1

sys_lenght's value indicates which option with the specified value is selected. Thus if you set sys_lenght.value to "80" it will select Value 3.
To change the value of the currently selected option you have to get a reference to that first. You can do so by getting the selectedIndex of sys_lenght, and then get the specific item from that index.
For Each Elementz In WebBrowser1.Document.GetElementsByTagName("select")
If Elementz.Name = "sys_lenght" Then
'Get the index of the selected option.
Dim SelectedIndex As Integer = Integer.Parse(Elementz.GetAttribute("selectedIndex"))
If SelectedIndex >= 0 Then
'Get the option element from the resulting index.
Dim SelectedOption As HtmlElement = Elementz.Children(SelectedIndex)
SelectedOption.setAttribute("value", "80")
Else 'No option selected.
MessageBox.Show("No option selected!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
Exit For 'We found what we were looking for; stop looping.
End If
Next

Answer 2

First you have to understand how html open and close tag, you forgot to close the html selection option open tag i mean the last greter sign > then use javascript query to find the value within the option example
WebControl1.ExecuteJavascript('document.querySelector('option [value='your value']').selected=true;")
hope its help?