I'm using Bootstrap v4 and bootstrap-select js/css (in ASP.NET MVC project) and I have a problem in my form. The select with multiple options from bootstrap-select is wider than the rest of my inputs, even though it's in a div with class="form-control".
The output looks something like this:

As you can see, Field Of Expertise dropdown is way larger then the rest of the inputs. I tried to edit bootstrap-select.css and change width:auto, but didn't work. Is there anything I can do to match the width of my other inputs?
My code looks something like this
<div class="form-group">
@Html.LabelFor(v => v.BirthDate)
@Html.TextBoxFor(v => v.BirthDate, "{0:yyyy-MM-dd}", new { @class = "form-control", type = "date" })
@Html.ValidationMessageFor(v => v.BirthDate)
</div>
<div class="form-group">
@Html.LabelFor(v => v.ResidenceCountry)
@Html.TextBoxFor(v => v.ResidenceCountry, new { @class = "form-control" })
@Html.ValidationMessageFor(v => v.ResidenceCountry)
</div>
<div class="form-group">
@Html.LabelFor(m => m.CurrencyId)
@Html.DropDownListFor(m => m.CurrencyId, new SelectList(Model.Currencies, "Id", "Name"), "", new { @class = "form-control" })
@Html.ValidationMessageFor(m => m.CurrencyId)
</div>
<div class="form-group">
@Html.LabelFor(m => m.FieldOfExpertiseIds)
@Html.ListBoxFor(m => m.FieldOfExpertiseIds, new MultiSelectList(Model.FieldOfExpertises, "Id", "Name"), new { @class = "selectpicker form-control", @data_selected_text_format = "count > 2", @data_size = "6" })
@Html.ValidationMessageFor(m => m.FieldOfExpertiseIds)
</div>
UPTADE:
I changed now the form-group to something like this (added @data_width = "auto"):
<div class="form-group">
@Html.LabelFor(m => m.FieldOfExpertiseIds)
<br />
@Html.ListBoxFor(m => m.FieldOfExpertiseIds, new MultiSelectList(Model.FieldOfExpertises, "Id", "Name"), new { @class = "selectpicker form-control", @data_selected_text_format = "count > 2", @data_size = "6" , @data_width="auto" })
@Html.ValidationMessageFor(m => m.FieldOfExpertiseIds)
</div>
