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.