Updating an Entity Without Saving the Data back to the Database - linq

Question

I have created a new query like the following
var pressData = from press in dataContext.Releases
select new
{
Heading = press.Heading,
Description = press.Desc,
DatePublished = press.PublishDate.ToString(),
Body = press.BodyContent,
ID=press.ReleaseID,
CreatedBy=press.CreatedBy
};
Later in the code I want to update the entity from a session variable, but not save any data back to the database. Here is the code I am trying to accomplish this with....
var edit = pressData.Where(a => a.Heading == sectionPreview.HeadingContent && a.ID == sectionPreview.tionID).FirstOrDefault();
if (edit != null)
{
//WONT LET ME UPDATE THE Body VALUE
edit.Body = sectionPreview.SectionContent;
}
The code aboves purpose is to look at pressData and replace the body content with the new body from a session variable(not shown here), but NOT save it to the db. I want pressData to be filtered and updated only in the entity. So when I bind it to the control in this case it binds the data stored in my session.
this.rptSections.DataSource = pressData;
this.rptSections.DataBind();
I am getting a complier error stating
Property or indexer 'AnonymousType#1.Body' cannot be assigned to -- it is read only.
I checked the entity model and nothing is read only not any fields not anything. I must be missing something?

Answer 1

Anonymous Types encapsulate a read only property collection - for more information, read here. The compiler rewrites anonymous types as a constructor injections, ie:
select new
{
Heading = press.Heading,
Description = press.Desc,
DatePublished = press.PublishDate.ToString(),
Body = press.BodyContent,
ID=press.ReleaseID,
CreatedBy=press.CreatedBy
};
Is really rewritten as:
new Anonymous`1(press.Heading, press.Desc, press.PublishDate.ToString(), press.BodyContent, press.ReleaseID, press.CreatedBy)
And the properties are read only (public get, private / protected set, to use an easy comparison). If you want to solve your issue, instead of taking the data and making an anonymous object, create a real type and set properties on it.