How do I maintain a selection in my MVC 5 view's dropdownlist after a postback?

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MVC

Razor

I have 2 dropdownlists of month and year. here is the razor code.

@using (Html.BeginForm("Index", "Expense", FormMethod.Get))
{
    <p>
        Month <select name="drpMonth">
            @for (var i = 1; i <= 12; i++)
            {

                <option>@i</option>
            }
        </select>
        Year <select name="drpYear">
            @for (var i = -3; i <= 3; i++)
            {
                <option>@(DateTime.Now.AddYears(i).Year)</option>
            }
        </select>
        <input type="submit" value="Filter" />

    </p>
}

when i click on "Filter" button, a postback occurs and the selected value of the dropdownlists are set to default.
How do I maintain a selection in my MVC 5 view's dropdownlist after a postback?