{"Object reference not set to an instance of an object."}

My View

-----------

@Html.LabelFor(model => model.PhysicalAddr, htmlAttributes: new { @class = "control-label", @style = "margin-left:10px; float:left;" })

@Html.EditorFor(model => model.PhysicalAddr, new { htmlAttributes = new { @class = "form-control", @style = "margin-left:150px;" } })
@Html.ValidationMessageFor(model => model.PhysicalAddr, "", new { @style = "color:red;!important; margin-left:150px;" })

model

--------------

public class PersonModel
{
public PersonModel()
{
marketService = new MarketModel();
//regionService = new RegionModel();
Region = new List();
}

[Required]
[Display(Name = "Region")]
public int RegionId { get; set; }
public List Region { get; set; }

}

Controller

-------------

public List GetRegionList()
{
var list = regionService.GetRegions();
List regionList = new List();
int tableRow = Convert.ToInt32(list.Tables.Count);

for (int i = 0; i < tableRow; i++)
{
foreach (DataRow dr in list.Tables[i].Rows)
{
regionList.Add(new RegionModel
{
RegionId = Convert.ToInt32(dr["RegionId"]),
RegionName = Convert.ToString(dr["RegionName"]),
State = Convert.ToString(dr["State"]),
ZipCode = Convert.ToInt32(dr["ZipCode"])
});
}
}
return regionList;
}