How to place a button beside a select List - html

Question

I am coding an MVC 5 view, and I want to place a button next to a select list. My current code places the button under the select list.
Here is my code:
<div class="form-group">
#Html.LabelFor(model => model.userName, htmlAttributes: new { #class = "control-label col-md-2" })
<div class="col-md-10">
#Html.DropDownListFor(m => m.userName, Model.userNames, htmlAttributes: new { #class = "form-control" })
<div class="col-md-offset-2 col-md-10">
<input type="submit" value="Select" class="btn btn-default" />
</div>
</div>
</div>
Here is an image showing the button placement:
Even if I have the following code, the button is under the select list:
<p>
#Html.LabelFor(model => model.userName, htmlAttributes: new { #class = "control-label col-md-2" })
#Html.DropDownListFor(m => m.userName, Model.userNames, htmlAttributes: new { #class = "form-control" }) <input type="submit" value="Select" class="btn btn-default" />
</p>

Answer 1

Don't put the submit button in a div.
A div is display: block by default.

Answer 2

<div class="input-group">
#Html.DropDownListFor(m => m.userName, Model.userNames, htmlAttributes: new { #class = "form-control" })
<span class="input-group-btn">
<input type="submit" value="Select" class="input-group-addon btn btn-default" />
</span>
</div>
By using the classes input-group on the div, input-group-btn on the span and input-group-addon on the select button , you can place dropdownlist and button on the same line.
Refer to this article :
https://www.tutorialrepublic.com/twitter-bootstrap-tutorial/bootstrap-input-groups.php