How to set first checkbox checked in mvc

Here i want to set the first checkbox checked.I am not understanding how,since its in a viewbag.

<div class="form-group">

@Html.LabelFor(m => m.RBO_Location, new { @class = "col-md-2 control-label" })
<div class="col-md-10">
        @foreach (var item in (SelectList)ViewBag.Branches)
      {  
      <div>
      <input type="checkbox" name="selectedBranches"          value="@item.Value" class="checkbox-inline" />
       @Html.Label(item.Text, new { @class = "control-label" })
           </div>
      }
  </div>
  </div>