Entity Framework issues - appends a "1" to my table name?

I have replicated your model exactly as you have listed it and I cannot currently reproduce your issue in the DDL that the EDMX surface emits when Generating Database from Model.

Could you please provide detailed information on exactly how you are going about adding your many-to-many relationship between DatabaseGroup and DatabaseSupporter? You say that you're trying to add the relationship on the edmx surface and NOT through code and it craps on your table name?

I added this thing Many-to-many from DatabaseGroup to DatabaseSupporter I added this thing Many-to-many from DatabaseSupporter to DatabaseGroup

Can you please provide the following:

Rollback to your codebase prior to adding the many-to-many relationship. Ensure that your EF Fluent API code is not currently in your project.

• Generate the DDL from this surface and confirm that it is not being generated with the name DatabaseSupporters1 (Post the tablename that it chooses at this stage. DatabaseSupporter or DatabaseSupporters)

Now, right click DatabaseGroup| Add New| Association

• Choose DatabaseGroup for the left and DatabaseSupporter for the right. Confirm that the name of the association that the designer chooses is DatabaseGroupDatabaseSupporter [Do not create]
• Choose DatabaseSupporter for the left and DatabaseGroup for the right. Confirm that the name of the association that the designer chooses is DatabaseSupporterDatabaseGroup [Create]

From the edmx surface, right click the many-to-many association just created and click "Show in Model Browser"

• Edit your post to include the settings that display.

Also, right click the surface and click "Generate Database from Model."

• Edit your post to include the DDL that gets generated. The table should be named [DatabaseSupporters]

(My first inclination is that it's going to have something to do with your navigation properties, but not entirely sure. I actually had Entity Framework do the same thing to me in a toy project I was working on but I recall it being trivial to correct and I don't recall what the root cause was; I seem to recall it being something about the nav properties)

[Edit] Wait.....

If I remove the many-to-many that doesn't fix my problem. However, reverting to before I added the many-to-many fixes it. The exact code that throws the exception is already shown. If I remove my fluent mappings entirely, it's not the same exception being thrown (it throws something about a group and a supporter, and a principal). I have not tried recreating the model in an empty project - that takes a lot of time. I already tried searching the EDMX in Notepad for references - none were found.

(note my added emphasis) So the DatabaseSupporter1 error showed up after you tried your fluent api patch? Get rid of the patch, add the many-to-many and give us the real error then.

...also, it took me 5 minutes to build this diagram. I wouldn't qualify that as "a lot of time."

This mapping is incorrect:

modelBuilder
    .Entity<DatabaseSupporter>()
    .Map(m =>
    {
        m.Property(s => s.Id)
            .HasColumnName("Id");
        m.ToTable("DatabaseSupporter");
    });

It is kind of 50 percent of a mapping for Entity Splitting - a mapping that stores properties of a single entity in two (or even more) separate tables that are linked by one-to-one relationships in the database. Because the mapping is not complete you even don't get a correct mapping for Entity Splitting. Especially EF seems to assume that the second table that contains the other properties (that are not explicitly configured in the mapping fragment) should have the name DatabaseSupporter1. I could reproduce that with EF 6 (which by the way has added a Property method to configure single properties in a mapping fragment. In earlier versions that method didn't exist (only the Properties method).) Also the one-to-one constraints are not created correctly in the database. In my opinion EF should throw an exception about an incorrect mapping here rather than silently mapping the model to nonsense without exception.

Anyway, you probably don't want to split your entity properties over multiple tables but map it to a single table. You must then replace the code block above by:

modelBuilder.Entity<DatabaseSupporter>()
    .Property(s => s.Id)
    .HasColumnName("Id");

modelBuilder.Entity<DatabaseSupporter>()
    .ToTable("DatabaseSupporter");

The first mapping seems redundant because the property Id will be mapped by default to a column with the same name. The second mapping is possibly also redundant (depending on if table name pluralization is turned on or not). You can try it without this mapping. In any case you shouldn't get an exception anymore that complains about a missing dbo.DatabaseSupporter1.

I don't have my dev environment here in front of me, but my immediate thoughts are:

FIRST

Your fluent looks ok - but is the plural s in your ID column correct? And no plural (s) on the table names? This would be the opposite of convention.

SECOND

EF will automatically append a number to address a name collision. See similar question here: Why does EntityFramework append a 1 by default in edmx after the database entities?

Any chance you have something hanging around - a code file removed from your solution but still in your build path? Have you tried searching your source folder using windows explorer rather than the visual studio?