Для выбранного источника данных не найдено поле или свойство с именем string

public List<Models_BrandDetails> GetModels(string brandOfCar)
        {
            SqlConnection connection = Connection.Create();
            SqlCommand cmd = new SqlCommand("GetModels_DDL", connection);
            cmd.CommandType = CommandType.StoredProcedure;
            ListModels = new List<Models_BrandDetails>();
            cmd.Parameters.Add(new System.Data.SqlClient.SqlParameter("BrandOfCar", System.Data.SqlDbType.NVarChar, 30));
            cmd.Parameters["BrandOfCar"].Value = brandOfCar;

            try
            {
                connection.Open();
                SqlDataReader reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    Models_BrandDetails modelsBrandDetails = new Models_BrandDetails((string)reader["nameModel"]);
                    ListModels.Add(modelsBrandDetails);
                }

                reader.Close();
                return ListModels;
            }
            catch (SqlException err)
            {
                throw new ApplicationException("Data error Get Brands.");
            }
            finally
            {
                connection.Close();
            }
        }

CREATE PROCEDURE GetModels_DDL
@brandOfCar nvarchar(30)
AS
SELECT nameModel FROM Models where brandId in (SELECT IdBrand From Brands where brandOfCar = @brandOfCar);

public class Models_BrandDetails
    {
            private string brandOfCar;
            private string model;            
            private int idBrand;

            public Models_BrandDetails()
            {

            }       
       
           
            public Models_BrandDetails(int brandId)
            {
                this.IdBrand = brandId;
            }

            public Models_BrandDetails(string brandOfCar)
            {
                this.BrandOfCar = brandOfCar;
            }            

            public string BrandOfCar
            {
                get { return brandOfCar; }
                set { brandOfCar = value; }
            }

            public string Model
            {
                get { return model; }
                set { model = value; }
            }
            
            public int IdBrand
            {
                get { return idBrand; }
                set { idBrand = value; }
            }
    }

Models_BrandDetails modelsBrandDetails = new Models_BrandDetails((string)reader["nameModel"]);

Ошибка сервера в приложении '/'.
Для выбранного источника данных не найдено поле или свойство с именем string.
Описание: Необработанное исключение при выполнении текущего веб-запроса. Изучите трассировку стека для получения дополнительных сведений о данной ошибке и о вызвавшем ее фрагменте кода.

Сведения об исключении: System.Web.HttpException: Для выбранного источника данных не найдено поле или свойство с именем string.

[HttpException (0x80004005): Для выбранного источника данных не найдено поле или свойство с именем string.]
   System.Web.UI.WebControls.BoundField.GetValue(Control controlContainer) +1763587
   System.Web.UI.WebControls.BoundField.OnDataBindField(Object sender, EventArgs e) +67
   System.Web.UI.Control.OnDataBinding(EventArgs e) +91
   System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +92
   System.Web.UI.Control.DataBind() +15
   System.Web.UI.Control.DataBindChildren() +201
   System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +101
   System.Web.UI.Control.DataBind() +15
   System.Web.UI.WebControls.GridView.CreateRow(Int32 rowIndex, Int32 dataSourceIndex, DataControlRowType rowType, DataControlRowState rowState, Boolean dataBind, Object dataItem, DataControlField[] fields, TableRowCollection rows, PagedDataSource pagedDataSource) +166
   System.Web.UI.WebControls.GridView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding) +3896
   System.Web.UI.WebControls.CompositeDataBoundControl.PerformDataBinding(IEnumerable data) +66
   System.Web.UI.WebControls.GridView.PerformDataBinding(IEnumerable data) +14
   System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data) +128
   System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +33
   System.Web.UI.WebControls.DataBoundControl.PerformSelect() +143
   System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +74
   System.Web.UI.WebControls.GridView.DataBind() +4
   System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +66
   System.Web.UI.WebControls.CompositeDataBoundControl.CreateChildControls() +75
   System.Web.UI.Control.EnsureChildControls() +102
   System.Web.UI.Control.PreRenderRecursiveInternal() +42
   System.Web.UI.Control.PreRenderRecursiveInternal() +175
   System.Web.UI.Control.PreRenderRecursiveInternal() +175
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2496

<asp:GridView ID="GridView1" runat="server" AllowPaging="True" 
            AutoGenerateColumns="False" BackColor="White" BorderColor="#3366CC" 
            BorderStyle="None" BorderWidth="1px" CellPadding="4" 
            DataSourceID="ObjectDataSource2" Height="253px" Width="246px">
            <Columns>
                <asp:BoundField DataField="string" HeaderText="Моделі :" 
                    SortExpression="Model" />
            </Columns>
            <FooterStyle BackColor="#99CCCC" ForeColor="#003399" />
            <HeaderStyle BackColor="#003399" Font-Bold="True" ForeColor="#CCCCFF" />
            <PagerStyle BackColor="#99CCCC" ForeColor="#003399" HorizontalAlign="Left" />
            <RowStyle BackColor="White" ForeColor="#003399" />
            <SelectedRowStyle BackColor="#009999" Font-Bold="True" ForeColor="#CCFF99" />
            <SortedAscendingCellStyle BackColor="#EDF6F6" />
            <SortedAscendingHeaderStyle BackColor="#0D4AC4" />
            <SortedDescendingCellStyle BackColor="#D6DFDF" />
            <SortedDescendingHeaderStyle BackColor="#002876" />
        </asp:GridView>
    </p>
    <p>
        <asp:ObjectDataSource ID="ObjectDataSource2" runat="server" 
            SelectMethod="GetModels" TypeName="AutoCatalog.Models_BrandDB">
            <SelectParameters>
                <asp:ControlParameter ControlID="DropDownList1" Name="brandOfCar" 
                    PropertyName="SelectedValue" Type="Object" />
            </SelectParameters>
        </asp:ObjectDataSource>