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POCannot apply migration
 

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    <p>I am trying to apply a migration to my database.</p> <p>Initially the DB was reverse-engineered to code first using the EF power-tools. in my database the table names all begin with tbl_[NAME] so after reverse engineering process completed I all the Models had this same convention. Since the model name is mapped to table name in the modelMAP for each model, I decided to rename all the generated models to remove the "tbl_" when I created the migration and had a look at the "UP" method, I could see that that EF wants to DropForeignKey on all affected tables, all the tables, then drop the tables!!! WHAT?</p> <p>Since my DB is large I will show only a few lines of code in the migration UP method.</p> <pre><code>DropForeignKey("dbo.tbl_AssetFileLocations", "AssetFileID", "dbo.tbl_AssetFiles"); DropForeignKey("dbo.tbl_AssetFileLocations", "StorageLocationID", "dbo.tbl_StorageLocations"); ... DROP ALL FOREIGN KEYS ON ALL TABLES ... DropIndex("dbo.tbl_AssetFileLocations", new[] { "AssetFileID" }); DropIndex("dbo.tbl_AssetFileLocations", new[] { "StorageLocationID" }); ... DROP ALL INDEXES ... CreateTable( "dbo.tbl_AssetFileLocations", c =&gt; new { AssetLocationID = c.Guid(nullable: false), AssetFileID = c.Guid(nullable: false), StorageLocationID = c.Guid(nullable: false), DateCreatedonStorage = c.DateTime(nullable: false), }) .PrimaryKey(t =&gt; t.AssetLocationID) .ForeignKey("dbo.tbl_AssetFiles", t =&gt; t.AssetFileID, cascadeDelete: true) .ForeignKey("dbo.tbl_StorageLocations", t =&gt; t.StorageLocationID, cascadeDelete: true) .Index(t =&gt; t.AssetFileID) .Index(t =&gt; t.StorageLocationID); ... CREATE ALL OTHER TABLES ... DropTable("dbo.tbl_AssetFileLocations"); ... DROP ALL TABLES ... </code></pre> <p>I have no data in the database so though I am not sure why EF has decided to drop all tables and recreate them it's not a problem in my experiment. However I would like to understand why changing the model names cause a full database rebuild (the new name maps to the same table name as when the DB was reverse engineered!)</p> <p><strong>My main issue</strong></p> <p>when attempting to apply the migration I end up in a circular error storm.</p> <p><strong>1st attempt gives error:</strong> FK_dbo.tbl_AssetFileLocations_dbo.tbl_AssetFiles_AssetFileID' is not a constraint. Could not drop constraint. See previous errors.</p> <p>So I think ok, I will comment out the DropForeignKey //DropForeignKey("dbo.tbl_AssetFileLocations", "AssetFileID", "dbo.tbl_AssetFiles");</p> <p>then it errors on the next dropForeignKey with the same (contextually) error. So as an experiment I comment out all the DropForeignKey statements.</p> <p>re-running the update-database command then results in the error message:</p> <p>Cannot drop the index 'dbo.tbl_AssetFileLocations.IX_AssetFileID', because it does not exist or you do not have permission.</p> <p>and one by one it complains about all DropIndex statements. So As an experiment I comment out all the and try to update-database</p> <p>So as we can see the next thing the UP method attempts to do is Add all the tables! Of course I get the error: There is already an object named 'tbl_AssetFileLocations' in the database.</p> <p>So I figure well EF your being a bit dull here, you are trying to drop the tables after you create them! so I change the order of the Drop table commands so that they come before the Create Table commands because that makes more sense. </p> <p>Since this is just an experiment with EF code first and migration it is all cool. I am happy for EF to delete the entire DB schema and rebuild it.</p> <p>So with the Drop Table commands now in the correct place, I re-run the Update-Database to get the final circular error:</p> <p>Could not drop object 'dbo.tbl_Assets' because it is referenced by a FOREIGN KEY constraint.</p> <p>And to myself I think "YES, that's the FOREIGN KEY constraint, you refused to drop at the beginning of this exercise.</p> <p>So where do I go from here. From this experiment it would appear that Code-First migrations don't work for all but the simple examples given on the EF website!</p> <p>Has anyone reverse engineered a large DB and been successful at making code changes and migrating those to the DB?</p> <p>Should I forget code-first and return to Database first (I'd rather not - I love the idea of code first)?</p> <p>Please help EF people.</p>
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    1. COWhile not exactly the answer to your whole question, the reverse engineering followed up with migrations caused me a bit of trouble too. See my question here and an awesome answer that might help somewhat: http://stackoverflow.com/questions/17736708/unable-to-run-ef5-migration-with-existing-database
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    2. COBasically, reverse engineer DB, add an EMPTY migration, and call update-database.
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