Massive list in c# & wpf

我有一个由所有美国邮政编码组成的列表，每个邮政编码有3个元素。因此，该列表约为45000 x 3个字符串。加载它的最佳方式是什么，本质上是最高效/优化的？现在我有一个foreach循环在运行它，每次它到达加载点时都会挂起。有更好的方法吗？

编辑

它的用途是让用户能够键入邮政编码，并在另外两个文本框中显示城市和州。现在我已经设置为在用户输入时进行检查，在输入污垢编号后，它会冻结，我相信在ZipCodes代码=新的ZipCodes（）

这是我目前正在使用的代码。我在中留下了一个zipCode.Add语句，但删除了其他44999。

struct ZipCode
{
    private String cvZipCode;
    private String cvCity;
    private String cvState;
    public string ZipCodeID { get { return cvZipCode; } }
    public string City { get { return cvCity; } }
    public string State { get { return cvState; } }
    public ZipCode(string zipCode, string city, string state)
    {
        cvZipCode = zipCode;
        cvCity = city;
        cvState = state;
    }
    public override string ToString()
    {
        return City.ToString() + ", " + State.ToString();
    }
}
class ZipCodes
{
    private List<ZipCode> zipCodes = new List<ZipCode>();
    public ZipCodes()
    {            
        zipCodes.Add(new ZipCode("97475","SPRINGFIELD","OR"));            
    }
    public IEnumerable<ZipCode> GetLocation()
    {
        return zipCodes;
    }
    public IEnumerable<ZipCode> GetLocationZipCode(string zipCode)
    {
        return zipCodes;
    }
    public IEnumerable<ZipCode> GetLocationCities(string city)
    {
        return zipCodes;
    }
    public IEnumerable<ZipCode> GetLocationStates(string state)
    {
        return zipCodes;
    }
}
private void LocateZipCode(TextBox source, TextBox destination, TextBox destination2 = null)
    {
        ZipCodes zips = new ZipCodes();
        string tempZipCode;
        List<ZipCode> zipCodes = new List<ZipCode>();
        try
        {
            if (source.Text.Length == 5)
            {
                tempZipCode = source.Text.Substring(0, 5);
                dataWorker.RunWorkerAsync();
                destination.Text = zipCodes.Find(searchZipCode => searchZipCode.ZipCodeID == tempZipCode).City.ToString();
                if (destination2.Text != null)
                {
                    destination2.Text = zipCodes.Find(searchZipCode => searchZipCode.ZipCodeID == tempZipCode).State.ToString();
                }
            }
            else destination2.Text = "";
        }
        catch (NullReferenceException)
        {
            destination.Text = "Invalid Zip Code";
            if (destination2 != null)
            {
                destination2.Text = "";
            }            
        }
    }