You need to create a list of _AccessionType and assign it to the DataSource property of the grid view.
List<_AccessionType> accessionTypes= new List<_AccessionType>();
// Add objects to the list
gridView1.DataSource = accessionTypes;
gridView1.DataBind();
In the designer for gridView1, you need to right click > Edit Columns and add Bound columns. For each bound column give a suitable HeaderText and in the DataField assign the required member property of _AccessionType (e.g. DocUrl)
You cannot retrieve the object from gridView.DataSource back into List<_AccessionType> or even from the GridViewRow into _AccessionType. Inorder to get the values for a grid view row back, you need to define data keys in the grid view for the values you need to retrieve back.
e.g.
<asp:GridView ID="gridView1" runat="server"
AutoGenerateColumns="False" DataKeyNames="AccessionId, DocUrl" EnableViewState="true">
...
</asp:GridView>
Later in the code, you can retrieve back these values when you loop through the DataGrid or in a related data grid event handler:
foreach (GridViewRow accessionRow in this.gridView1.Rows)
{
int accessionID = Convert.ToInt32(gridView1.DataKeys[accessionRow.RowIndex]["AccessionId"]);
}