I am trying to populate a GridView
using Entity Frameworkm but every time I am getting the following error:
"Property accessor 'LoanProduct' on object 'COSIS_DAL.MemberLoan'
threw the following exception: The ObjectContext instance has been
disposed and can no longer be used for operations that require a
connection."
My code is:
public List<MemberLoan> GetAllMembersForLoan(string keyword)
{
using (CosisEntities db = new CosisEntities())
{
IQueryable<MemberLoan> query = db.MemberLoans.OrderByDescending(m => m.LoanDate);
if (!string.IsNullOrEmpty(keyword))
{
keyword = keyword.ToLower();
query = query.Where(m =>
m.LoanProviderCode.Contains(keyword)
|| m.MemNo.Contains(keyword)
|| (!string.IsNullOrEmpty(m.LoanProduct.LoanProductName) && m.LoanProduct.LoanProductName.ToLower().Contains(keyword))
|| m.Membership.MemName.Contains(keyword)
|| m.GeneralMasterInformation.Description.Contains(keyword)
);
}
return query.ToList();
}
}
protected void btnSearch_Click(object sender, ImageClickEventArgs e)
{
string keyword = txtKeyword.Text.ToLower();
LoanController c = new LoanController();
List<COSIS_DAL.MemberLoan> list = new List<COSIS_DAL.MemberLoan>();
list = c.GetAllMembersForLoan(keyword);
if (list.Count <= 0)
{
lblMsg.Text = "No Records Found";
GridView1.DataSourceID = null;
GridView1.DataSource = null;
GridView1.DataBind();
}
else
{
lblMsg.Text = "";
GridView1.DataSourceID = null;
GridView1.DataSource = list;
GridView1.DataBind();
}
}
The error is mentioning the LoanProductName
column of the Gridview
. Mentioned: I am using C#, ASP.net, SQL-Server 2008 as back end DB.
I am quite new to Entity Framework. I can't understand why I am getting this error. Can anyone help me please?
Best Answer
By default Entity Framework uses lazy-loading for navigation properties. That's why these properties should be marked as virtual - EF creates proxy class for your entity and overrides navigation properties to allow lazy-loading. E.g. if you have this entity:
Entity Framework will return proxy inherited from this entity and provide DbContext instance to this proxy in order to allow lazy loading of membership later:
So, entity has instance of DbContext which was used for loading entity. That's your problem. You have
using
block around CosisEntities usage. Which disposes context before entities are returned. When some code later tries to use lazy-loaded navigation property, it fails, because context is disposed at that moment.To fix this behavior you can use eager loading of navigation properties which you will need later:
That will pre-load all memberships and lazy-loading will not be used. For details see Loading Related Entities article on MSDN.