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How to save correctly new data with working copy approach

In my application every user can add a new book. There is possibility to add a photo of the book. All fields in form are mandatory but if user wants to finish this form later, he can save half of form as working copy. I wonder how I need to build the working copy function that will save only new photos of the books and remove old.
Entities:
-Book
*Id [PK]
*Title
*Author
*Description
*PagesCount
-BookPhotos
*Id [PK]
*BookId [FK]
*BookPhoto [string base64]
I have a couple of ideas, but I need to choose one (or maybe find diffrent) with the best optimization:
Every time delete all photos which are connected to the edited Book entity.
Try to find the same value in field BookPhoto [base64] and edit only this field in the database.
Edit every record in the table (to the new BookPhoto data) that BookPhoto [base64] didn't exist in edit request data.
In my opinion:
I wonder if the database wouldn't be angry at me if I will remove and insert a new data into the table with every request. Is there will be any problem with that approach? What if this will do a hundred or thousands of people?
This sounds nice but what if edit data won't contain old BookPhoto value? Then I need to remove every record from the table that didn't exist in request edit (working copy) data.
I think that there will be a lot of problems with editing and comparing. For example what if the request data will have less photos than exist in table. Which one will be edited with which.
If someone have some ideas how to do this in the correct way I will be thankful.
Best Regards :)

Compare BookPhotos.Id
Select the BookPhotos of the working-set's Book from the database. For each DB photo:
If ID is in working-set, then update the bytes (base64 string in your case)
If ID is not in working-set, then delete the photo
For each working-set photo:
If ID is not in DB, then insert that photo as new
Alternatively, the web request can specify which records are new, modified, and removed, instead of just supplying the new state of the model. Then you simply perform those actions against the DB.
A con to this is that you are trusting the client. If it says to add an already existing item (primary key) or modify/delete an item that does not exist, of course the DB operation will fail. You decide how to respond to the client in that case, and if you will rollback all operations as a single transaction or allow what worked to be committed.

Implementing array like structure in MySQL database

I'm currently trying to implement a table within my SQL database. I'm looking to create a table that can be used to check if a user on my website has liked a post. The idea is to have a table with one axes iterating the posts on the website and one axis with the userID values iterated. Then in each box hold a binary value as to whether they have liked it. I'm just wondering how I would implement this. I have been doing this in C# by creating classes and converting these into server side code using Entity Framework 6.4.0.
Any help would be great.

What you are suggesting is a normalized structure for your use case; it would, for example, require adding more columns to the table everytime a post is added to the database (or a user, depending on whether you use rows or columns).
A typical database solution would be a bridge table, that represents the many to many relationship between posts and users.
Say table user_like_posts, with the following columns:
user_id -- foreign key to the "users" table
post_id -- foreign key to the "posts" table
You may want to add additional columns to the bridge table, like the timestamp when the user liked the post, or the-like.

Will every user have an opinion on every post? If not then you don't have the data you described. If users and posts are not related one to one then you have a simple relation. For each post that a user likes (or dislikes?) there is an entry for that user:
Likes/Dislikes Table:
User identifier
Post identifier
The binary value that indicates like or dislike
If the table only indicates 'likes' then you don't need the last column.
A design like this would work even if every user and every post is in this table. The table might get large in a hurry and keep growing every time you introduced a new post. But if this table only includes actual 'likes' (and/or 'dislikes') it should be manageable.
For a class you just have an enumerable that has the posts 'liked' (and possibly another that indicates the posts 'disliked.')
Think about what you are trying to represent. Ask yourself questions. Don't just latch on to an idea and try to 'do' it.
Will every user have an opinion of every post?
Do you need to store both 'likes' and 'dislikes?'
Can there be a 'neutral' opinion on a post?
Can users change their opinions?
You can only discover the correct data structure by asking and answering all the questions that matter to your situation (my list is not exhaustive - it is only an example.)

Remove list values based on series of other values

I have a situation wherein a List object is built off of values pulled from a MSSQL database. However, this particular table is mysteriously getting an errant record or two tossed in. Removing the records cause trouble even though they have no referential links to any other tables, and will still get recreated without any known user actions taken. This causes some trouble as it puts unwanted values on display that add a little bit of confusion. The specific issue is that this is a platform that allows users to run a search for quotes, and the filtering allows for sales rep selection. The select/dropdown field is showing these errant values, and they need to be removed.
Given that deleting the offending table rows does not provide a desirable result, I was thinking that maybe the best course of action was to modify the code where the List object is created and either filter the values out or remove them after the object is populated. I'd like to do this in a clean, scalible fashion by providing some kind of appendable data object where I could just add in a new string value if something else cropped up as opposed to doing something clunky that adds new code to find the value and remove it each time.
My thought was to create a string array, and somehow loop through that to remove bad List values, but I wasn't entirely certain that was the best way to approach this, and I could not for the life of me think of a clean approach for this. I would think that the best way would be to add a filter within the Find arguments, but I don't know how to add in an array or list that way. Otherwise I figured to loop through the values either before or after the sorting of the List and remove any matches that way, but I wasn't sure that was the best choice of actions.
I have attached the current code, and would appreciate any suggestions.
int licenseeID = Helper.GetLicenseeIdByLicenseeShortName(Membership.ApplicationName);
List<User> listUsers;
if (Roles.IsUserInRole("Admin"))
{
//get all users
listUsers = User.Find(x => x.LicenseeID == licenseeID).ToList();
}
else
{
//get only the current user
listUsers = User.Find(x => (x.LicenseeID == licenseeID && x.EmailAddress == Membership.GetUser().Email)).ToList();
}
listUsers.Sort((x, y) => string.Compare(x.FirstName, y.FirstName));
-- EDIT --
I neglected to mention that I did not develop this, I merely inherited its maintenance after the original developer(s) disappeared, and my coworker who was assigned to it left the company. I'm not really really skilled at handling ASP.NET sites. Many object sources are hidden and unavailable for edit, I assume due to them being defined in a DLL somewhere. So, for any of these objects that are sourced from database tables, altering the tables will not help, since I would not be able to get the new data anyway.
However, I did try to do the following to filter out the undersirable data:
List<String> exclude = new List<String>(new String[] { "value1" , "value2" });
listUsers = User.Find(x => x.LicenseeID == licenseeID && !exclude.Contains(x.FirstName)).ToList();
Unfortunately it only resulted in an error being displayed to the page.
-- EDIT #2 --
I got the server setup to accept a new event viewer source so I could write info to the Application log to see what was happening. Looks like this installation of ASP.NET does not accept "Contains" as an action on a List object. An error gets kicked out stating that the method is not available.

I will probably add a bit to the table and flag Errant rows and then skip them when I query the table, something like
&& !ErrantData
Other way, that requires a bit more upkeep but doesn't require db change, would be to keep a text file that gets periodically updated and you read it and remove users from list based on it.
The bigger issue is unknown rows creeping in your database. Changing user credentials and adding creation timestamps may help you narrow down the search scope.

Linq to SQL, Update a lot of Data before One Insert

Before insert new value to table, I need change one field in all rows of that table.
What the best way to do this? in c# code, ore use trigger? if C# can you show me the code?
UPD
*NEW VERSION of Question*
Hello. Before insert new value to table, I need change one field in all rows of that table with specific ID( It is FK to another table).
What the best way to do this? in c# code, ore use trigger? if C# can you show me the code?

You should probably consider changing your design this doesn't sound like it will scale well, i would probably do it with a trigger if it is always required, but if not, id use ExecuteCommand.
var ctx = new MyDataContext();
ctx.ExecuteCommand("UPDATE myTable SET foo = 'bar'");

Looking at your comment on Paul's answer, I feel like I should chime in here. We have a few tables where we need to keep a history of each entry in that table. We implement this by creating a separate table for each. For example, we may have a Comment table, and then a CommentArchive table with a foreign key reference to the CommentId in the Comment table.
A trigger on the Comment table ensures that each time certain fields in the Comment table are updated, the "old" version (which is accessible via the deleted table in the trigger) gets pushed to the CommentArchive table. Obviously, this means several CommentArchive entries may exist for each Comment, but if you're only looking for the "active" comments, you just look in the Comment table. And if you need information about the history of a comment, you can easily use LINQ to SQL to jump from the Comment you're interested in to the CommentArchives that reference it.
Because the triggers we use in the above example only insert a single value into the Archive table for each update, they run very quickly and we get good performance. We had issues recently where I tried making the triggers more complex and we started getting dead-locks with as few as 15 concurrent transactions. So the lesson is that you should make these triggers simple, and make them touch as few rows in as few tables as possible.

Getting more than one item from a database in ASP .NET MVC 3

I'm creating a database where users can enter some Error Reports and we can view them. I'm making these database with C# in the ASP MVC 3 .NET framework (as the tags imply). Each Error Report has a unique ID, dubbed ReportId, thus none of them are stored under the same Id. However, whenever a User creates a new Error, I pass their User Name and store it in with the rest of the report (I use User.Identity.Name.ToString() to get their name and store it as a string). I know how to get a single item from the data using a lambda expression, like so:
db.DBSetName.Single(g => g.Name == genre)
The above code is based on an MVC 3 tutorial (The Movie Store one) provided by ASP. This was how they taught me how to do it.
My major question is: is there a member function like the .Single one that will parse through the whole database and only output database entries whose stored User Name matches that of the currently logged in user's? Then, I can use this to restrict User's to being only able to edit their own entries, since only their entries would be passed to the User's View.
What would be the best way to implement this? Since the ReportId will not be changed, a new data structure can be created to store the user's Errors and passed through to the Index (or Home) View of that particular controller. From there they should be able to click any edit link, which will pass the stored ReportId back to the Edit Action of this particular controller, which can then search the entire database for it. Am I right in assuming this would work? And would this be ideal, given that the other items in the database are NOT passed through to the Index in this method, meaning the User does not have access to the other items' ReportId's, which the user needs to pass into the Edit Action for it to work? If this is ideal, this is the method that requires me to know how to parse through a database and grab every element that fits a particular description (stored User Name matches User's current User Name).
Or would a better approach be to pass the whole database to the Index View and only output the database entries that have User Name values that match the current logged in user's? I guess this could be done in a foreach loop with a nested if loop, like so:
#foreach(var item in db.Reports)
{
if(item.UserName == User.Identity.Name.ToString())
{
...code to output table...
}
}
But this passes the whole database which gives the user a lot more info than they need. It also gives them potential access to info I don't want them to have. However, I don't have to make a new data structure or database, which should lower server memory usage and fetch time, right? Or are databases passed by copy? If so, this method seems kinda dumb. However, I don't know if the first method would fracture the database potentially, this one certainly would not. Also don't remember if I NEED an else statement in C#, I'm more familiar with C++, where you don't need one and you also don't need {}'s for single line if's, if I need one: please don't judge me too harshly on it!
Small note: I am using CRUD Controllers made with the Entity First Framework in order to edit my database. As such, all creation, reading, updating, and deletion code has been provided for me. I have chosen not to add such basic, common code. If it is needed, I can add it. I will add what the Edit Action looks like:
public ActionResult Edit(string id)
{
Report report = db.Reports.Find(id);
return View(report);
}
It accepts a string as an id, ReportId is the id used and it IS a string. It is a randomly generated GUID string made with the GUID.NewGuid().ToString() function. I will also be doing the comparison of names with:
Model.UserName == User.Identity.Name.ToString()
Which was shown earlier. Sorry if this is too much text, I wanted to provide as much info as possible and not make anyone mad. If more info is needed, it can certainly be provided. So at the end of the post, the major question actually comes down to: which of the above two methods is best? And, if it's the first one, how do I implement something like that?
Thanks for your help!

Unless I'm completely misunderstanding you, you just want .Where()
Like this:
var reports = db.Reports.Where(r => r.genre == inputGenre);
This would get you an IEnumerable of Report, which you could then use however you wish.