更新数据库后，无法将文件“ .mdf”附加为数据库“ aspnet”

Question

Every time I want to update database after migration the error in the title occurs. My code is below:

Charity class:

public class Charity
{
    public int ID { get; set; }
    [StringLength(60, MinimumLength = 3, ErrorMessage = "There must be a name")]
    public string DisplayName { get; set; }
    [DisplayFormat(DataFormatString = "{dd-MM-yyyy}")]
    public DateTime Date { get; set; }
    [Range(2, Int32.MaxValue, ErrorMessage = "The must be greater than £2")]
    public Double Amount { get; set; }
    public Double TaxBonus { get; set; }
    [StringLength(20, MinimumLength = 4, ErrorMessage = "Please leave a comment")]
    public String Comment { get; set; }
}

public class CharityDBContext : DbContext //controls information in database 
{
    public DbSet<Charity> Donations { get; set; } //creates a donation database
}

web.config :

<connectionStrings>
    <add name="DefaultConnection" 
         connectionString="Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\aspnet-CharitySite-20160222115154.mdf;Initial Catalog=aspnet-CharitySite-20160222115154;Integrated Security=True"  
         providerName="System.Data.SqlClient" />
    <add name="CharityDBContext" 
         connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\Donations.mdf;Integrated Security=True" 
         providerName="System.Data.SqlClient" /> 
</connectionStrings>
<startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>

Server error:

The model backing the 'CharityDBContext' context has changed since the database was created. Consider using Code First Migrations to update the database

When running the program it states the server error to use first migration, all the steps work perfectly until the very last step which is 'update-database' it displays the error in the title. The reason it asks me to perform migration is because I validated a few things in the model.

Answer 1

You need to update your DB to match the models in your program. try this in these commands( under tools ->NugetPackage Manager -> package manager console) :

• Add-Migration 'give it a name' name it something signofocant to you, something like "updatedmodels" or something like that
• update-database

Answer 2

If you did not enable migrations, in the nuget package manager console, type:

enable-migrations (run this just once)

add-migration (use this every time you make a change)

update-database (use this to apply the new changes)