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PODatabase-first approach and modifying the database schema
 

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    <p>I am building an ASP.NET MVC web application using entity framework DbContext using the database first approach.</p> <p>If under certain conditions I needed to modify the database such as adding new table or modifying an existing table (adding columns or changing a column data type), should I:</p> <ol> <li>Remove the existing entity .edmx and .tt folders and re-create the mapping again</li> <li>Manually apply the modification to the model classes under the .tt folder after modifying the database</li> <li>Neither of these two options are valid.</li> </ol> <p>How should I approach the task of modifying my database schema?</p> <p><strong>Edited</strong> For example i have the following partial class which were automatically created under the .tt folder, baring in mind that i have added the <strong>*<em>IsManagedBy</em>*</strong> helper methodand the [MetadataType(typeof(Books_validation))] to it :-</p> <pre><code>[MetadataType(typeof(Books_validation))] public partial class Book { public Book() { this.Assessments = new HashSet&lt;Assessment&gt;(); this.Users_Books = new HashSet&lt;Users_Books&gt;(); } public int BookID { get; set; } public string BookName { get; set; } public string ManagedBy { get; set; } public byte[] Timestamp { get; set; } public virtual ICollection&lt;Assessment&gt; Assessments { get; set; } public virtual User User { get; set; } public virtual ICollection&lt;Users_Books&gt; Users_Bookes { get; set; } public bool IsManagedBy(string userName) { return ManagedBy.Equals(userName, StringComparison.OrdinalIgnoreCase); } } </code></pre> <p>And then i create the Book_validation class to apply the data annotations as following:-</p> <pre><code>public class Books_validation { [Required(ErrorMessage = "Name is required")] public string BookName { get; set; } public string ManagedBy { get; set; } [ConcurrencyCheck] [Timestamp] public Byte[] Timestamp { get; set; } } </code></pre> <p>This approach is causing three problems:-</p> <p><strong>1.</strong> The IsManagedBy helper method cannot be defined in the Book_validation class and i should define it in the automatically generated Book partial class , which means it will be removed if i regenerate the code !!!.</p> <p><strong>2.</strong> If for example i modify the Assessment table which is related to the Book class (by Foreign key ) and then i chose the “Update Model from Database” option from the .edmx designer; then visual studio will also regenerate the Book class , which will cause more troubles for me.</p> <p><strong>3.</strong> Even the [MetadataType(typeof(Books_validation))] which i wrote in the automatically generated code will also be removed in case i regenerate the code, so this means that i have to go over all the modified classes and add the associated MetadataType(typeof) for them.</p> <p>All these problems were not happening when i was using the ObjectContext template, since the ObjectContext template will not automatically generate partial classes , it will only generate model classes and then i can add partial classes and the metadatetype for them... so i think it is better to return back to ObjectContext instead of DBContext !!!, any suggestion on this and the above problems? BR</p>
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