var Data = [{"key": "key5", "value": "value5"}, {"key": "key4", "value": "value4"}, {"key": "key3", "value": "value3"}];

    var html = [];

    html.push('<select name="test">');

    for (var i = 0; i < Data.length; i++) {

        html.push('<option value="' + Data[i]["key"] + '">',

            Data[i]["value"],

            "</option>");

    }

    html.push('</select>');

    return html.join('');

        List<string> listOfString = new List<string>();

        for (int i = 0; i < 10; i++)

        {

            listOfString.Add(i.ToString());

        }

        string strResult = string.Join(", ", listOfString.ToArray());