How to selected drowndown list options in web browser

[C# Programming]

Hi there,

Im working a web browser automation project. There is an ajax controlled dropdown list in a web site.

It was like this;

test1
test2
test3
test4
test5


When i was selected test2 ajax is working and its giving another div. (I need this div)

I use this codes;

webbrowser1.Document.GetElementsByTagName("select")[0].Document.GetElementsByTagName("option")[1].SetAttribute("selected", "selected");


Its only changing attribute and for this reason it doesnt working ajax.

How can i select option 1?

Thanks.