Setting value of a textbox

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C#

I have to texboxes, that I cant manage to set text into. I tried making a function SetText("name" "details" "Hello"); But it doesnt work. Any ideas?
1st

<textarea name="details" id="details" cols="35" wrap="physical" rows="1"  önfocus="this.style.height='55px';" style="width: 300px; height: 55px;"></textarea>

2nd

<textarea id="sText" cols="50" rows="5" name="sText"></textarea>

void SetText(string attribute, string attName, string value)
        {


            Skybound.Gecko.GeckoElementCollection tagsCollection = ((Skybound.Gecko.GeckoWebBrowser)(tabControl2.SelectedTab.Controls[0])).Document.GetElementsByTagName("input");

            foreach (Skybound.Gecko.GeckoElement currentTag in tagsCollection)
            {

               // MessageBox.Show(currentTag.GetAttribute(attribute));
                // If the attribute of the current tag has the name attName

                if (currentTag.GetAttribute(attribute).Equals(attName))
                {
                   
                    // Then set its attribute "value".

                    currentTag.SetAttribute("value", value);
                    
                    currentTag.Focus();
                }
            }



            //  SendKeys.Send("{ENTER}");

        }