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I'm getting this exception:

The model backing the 'database' context has changed since the database was created. Consider using Code First Migrations to update the database (http://go.microsoft.com/fwlink/?LinkId=238269).

As I have been told, that error comes when you change you model that represents the tables of you database and your database have not the same attributes(tables and fields)(correct me if I'm wrong).

Tbl_Users, which is in the database, has the following structure

dbUser(int,not null)//key
dbUserId(varchar(50),null)//allow null, right?
dbPassWord(varchar(20),null)

This is the model:

public class Tbl_Users {
    [Key,DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int dbUser { get; set; }
    [MaxLength(50)]
    public string dbPassWord { get; set; }
    [MaxLength(20)]
    public string dbUserID{ get; set; }
    public int? dbLock { get; set; }
}

How can I set public string dbPassWord { get; set; } and public string dbPassWord { get; set; } to allow nulls? Or is there any other solution for this error?

Update

If I add a migration, and I update the database with Update-Database as told here, will the values of the affected table be erased?

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  • 3
    You appear to be trying to declare two properties called dbPassWord. Aside from the odd capitalization of both d and w, you can't declare two properties with the same name. And then there's the lack of dbUserId in your property list, and the lack of dbLock in your model... Commented Mar 25, 2013 at 19:22
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    @Kevin: No not string? as an example. string is already nullable as it's a reference type. Commented Mar 25, 2013 at 19:23
  • I just copied twice the dbPassword field. Sorry, the post have been updated. Commented Mar 25, 2013 at 19:24
  • 1
    backup your data and try:) Commented Mar 25, 2013 at 19:48

4 Answers 4

Reset to default
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As Jon Skeet's comment string is a nullable type.

public string MyProperty{get;set;}

MyProperty = null; //this is fine
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If i add a migration, and i update the database with Update-Database command as told here. Will the values of the afected table be erase?

Changing column to 'nullable' (providing it's not an index) or adding new columns (your dbLock) - should not delete data. And most of the time EF/CF migrations are to be trusted to do just the minimal changes on your existing Db structure - of course depending on what you did change (I'd be careful with renaming etc.).

Anyways, do the Add-Migration - and look up the migration file created (.cs - opens automatically for you) - it tells you what's in the up and down sections. You can recheck here what's EF doing for you.

And as suggested, backup first - and you're safe.

Other than that - even though Code First (via migrations) is made to adapt to changes to your objects - it's to be used during prototyping and development mostly - and minimize such changes in any production environment, as things will get more problematic.

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Is it maybe that your MaxLength attributes have been switched? They don't match the database:

public class Tbl_Users {

        [Key,DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int dbUser { get; set; }
        [MaxLength(20)]
        public string dbPassWord { get; set; }
        [MaxLength(50)]
        public string dbUserID{ get; set; }
        public int? dbLock { get; set; }
    }
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2 Comments

No, maxlength are the same.
If i add a migration, and i update the database with Update-Database command as told <a href="blogs.msdn.com/b/adonet/archive/2012/02/09/…>. Will the values of the afected table be erase?
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It is as best as I can tell, complaining that you don't have a dbLock column in your backing store(database). You need to enable Code First migrations, and then update the database. Or if you don't have data yet just push the update, but you'll almost certainly want Migrations eventually.

Pretty much what the Error message says.

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2 Comments

If i add a migration, and i update the database with Update-Database command as told <a href="blogs.msdn.com/b/adonet/archive/2012/02/09/…>. Will the values of the afected table be erase?
Not if you've enabled migrations. It is kind of the whole point. (And why EF was kinda broken without it) (Though do backup things just in case)