@{
    Layout = "~/Views/Shared/EditorTemplates/_FieldLayout.cshtml";
    var inputSize = (string)ViewData.ModelMetadata.AdditionalValues["InputSize"];
}
@if (!string.IsNullOrEmpty(inputSize))
{
    @Html.TextBox("", ViewData.TemplateInfo.FormattedModelValue, new { @class = inputSize})
}
else
{
    @Html.TextBox("", ViewData.TemplateInfo.FormattedModelValue)
}