The EntityKey property can only be set when the current value of the property is null with n-tier web applicaiton - asp.net

Question

I am working with n-tier web application with Entity Framework with ObjectDataSource.
In my web application there are Complains & WorkOrder entities which has many to one or zero relationship.
When a WorkOrder is added user can select for which complain it is for. This is what i tried to do.
<asp:DetailsView ID="DVComplain" runat="server"
DefaultMode="Insert" AutoGenerateInsertButton="True"
AutoGenerateRows="False" DataSourceID="ODSAddWorkOrder"
oniteminserting="DetailsView1_ItemInserting" >
<Fields>
<asp:TemplateField HeaderText="Complain">
<InsertItemTemplate>
<asp:DropDownList ID="DDLComplain" runat="server" DataTextField="ComplainID"
DataValueField="ComplainID" DataSourceID="EDSComplains"
oninit="DDLComplain_Init">
</asp:DropDownList>
<asp:CheckBox ID="CBIsWOOfComplain" runat="server"
oninit="CBIsWOOfComplain_Init" />
<asp:EntityDataSource ID="EDSComplains" runat="server"
ConnectionString="name=MMEntities" DefaultContainerName="MMEntities"
EnableFlattening="False" EntitySetName="ComplainMasters"
EntityTypeFilter="ComplainMaster" Select="it.[ComplainID]" OrderBy="it.ComplainID">
</asp:EntityDataSource>
</InsertItemTemplate>
</asp:TemplateField>
<asp:BoundField HeaderText="WOGeneratedDate" DataField="WOGeneratedDate" DataFormatString="yyyy-MM-dd" />
.......
</Fields>
</asp:DetailsView>
<asp:ObjectDataSource ID="ODSAddWorkOrder" runat="server"
DataObjectTypeName="MiantenanceManager.DAL.WorkOrder" TypeName="MiantenanceManager.BLL.WorkOrderBL"
InsertMethod="addWorkOrder">
</asp:ObjectDataSource>
And add the following code to DetailView ItemInserting method.
protected void DVWorkOrder_ItemInserting(object sender, DetailsViewInsertEventArgs e)
{
if (_CBIsWOOfComplain.Checked)
{
using (complainBL)
{
e.Values["Complain"] = complainBL.getComplianByID(_DDLComplains.SelectedValue);
}
}
}
Note: complainBL implements the IDispose.
In WorkOrederBL call it calls the WorkOrderRepository class which invokes the following method which throws the exception mention in the subject.
context.WorkOrder.AddObject(workOrder);
context.SaveChanges();
How can i overcome this problem. Is my approch is wrong??

Answer 1

The reason why you are getting thi serror is thet AddObject is for adding new objects. An object that has an entity key represents an existing row in the database. This assumes that you are using database generated keys for your tables.
There are different ways to fix it, for example:
Option 1: Get the record from the database, update the fields on that record, then save changes.
Option 2: Create a new object with the entity key, attach it to the context with state modified, then save changes.