blocks|key|84208|text|重新创建数据库。不要删除它，你的应用程序应该会继续工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|84209|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Recreate your database. Do not delete it and your app should continue to work.

blocks|key|84219|text|从应执行此操作的连接字符串中删除此行;)+"AttachDbFilename=%7CDataDirectory%7Cwhateverurdatabasenameis-xxxxxxxxxx.mdf“|type|unstyled|depth|inlineStyleRanges|entityRanges|data|84220|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Remove this line from the connection string that should do it ;)
"AttachDbFilename=|DataDirectory|whateverurdatabasenameis-xxxxxxxxxx.mdf"

blocks|key|301728|text|我认为对于SQL+Server+Local+Db，您不应该使用Initial+Catalog属性。我建议使用：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|301729|<add+name="DefaultConnection"+
+++++connectionString="Data+Source=(LocalDb)\v11.0;Integrated+Security=SSPI;AttachDBFilename=%7CDataDirectory%7C\OdeToFoodDb.mdf"+
+++++providerName="System.Data.SqlClient"+/>|code-block|syntax|javascript|301730|我认为本地数据库不支持同一mdf文件上的多个数据库，因此不支持指定一个初始目录(或者不是很好地支持，我有一些奇怪的错误)。|301731|entityMap^0|V|F|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

I think that for SQL Server Local Db you shouldn't use the <code>Initial Catalog</code> property.
I suggest to use:

<pre><code>&lt;add name="DefaultConnection" 
 connectionString="Data Source=(LocalDb)\v11.0;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\OdeToFoodDb.mdf" 
 providerName="System.Data.SqlClient" /&gt;
</code></pre>

I think that local db doesn't support multiple database on the same mdf file so specify an initial catalog is not supported (or not well supported and I have some strange errors).

blocks|key|84266|text|根据@davide-icardi，从web.config中删除"Initial+Catalog=xxx;“，但也要检查您的azure发布配置文件以将其从此处删除：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|84267|YourAspNetProject+path\Properties\PublishProfilesYourAspNetProjectName.pubxml|84268|<PublishDatabaseSettings>
++<Objects+xmlns="">
++++<ObjectGroup+Name="YourAspNetProjectName"+Order="1"+Enabled="True">
++++++<Destination+Path="Data+Source=AzureDataBaseServer;Initial+Catalog=azureDatabase_db;User+ID=AzureUser_db_sa@AzureDataBaseServer;Password=test"+/>
++++++<Object+Type="DbCodeFirst">
++++++++<Source+Path="DBMigration"+DbContext="YourAspNetProjectName.Models.ApplicationDbContext,+YourAspNetProjectName"+MigrationConfiguration="YourAspNetProjectName.Migrations.Configuration,+YourAspNetProjectName"+Origin="Configuration"+/>
++++++</Object>
++++</ObjectGroup>
++</Objects>
</PublishDatabaseSettings>|code-block|syntax|javascript|84269|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

As per @davide-icardi, remove the "Initial Catalog=xxx;" from web.config, but also check for your azure publish profile file to remove it from here too: 
[YourAspNetProject path]\Properties\PublishProfiles[YourAspNetProjectName].pubxml

<pre><code>&lt;PublishDatabaseSettings&gt;
 &lt;Objects xmlns=""&gt;
 &lt;ObjectGroup Name="YourAspNetProjectName" Order="1" Enabled="True"&gt;
 &lt;Destination Path="Data Source=AzureDataBaseServer;Initial Catalog=azureDatabase_db;User ID=AzureUser_db_sa@AzureDataBaseServer;Password=test" /&gt;
 &lt;Object Type="DbCodeFirst"&gt;
 &lt;Source Path="DBMigration" DbContext="YourAspNetProjectName.Models.ApplicationDbContext, YourAspNetProjectName" MigrationConfiguration="YourAspNetProjectName.Migrations.Configuration, YourAspNetProjectName" Origin="Configuration" /&gt;
 &lt;/Object&gt;
 &lt;/ObjectGroup&gt;
 &lt;/Objects&gt;
&lt;/PublishDatabaseSettings&gt;
</code></pre>

blocks|key|301782|text|我也犯了同样的错误。奇怪的是，我有一个新的项目从头开始，在那里它工作得很完美，还有另一个更大的项目，我总是遇到那个错误消息。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|301783|完美工作的项目(几乎)总是自动创建数据库(包括文件)。它可以是任何命令，读，写，更新。将创建这些文件。当然，它使用|301784|DropCreateDatabaseIfModelChanges|code-block|syntax|javascript|301785|当它遇到问题时，只有一种情况:如果mdf是自动创建的，而您删除了mdf和日志文件。那就差不多了。跟你的自动创造说再见吧。|301786|我找到的修复它的唯一方法是：|301787|sqllocaldb+stop+v11.0+&+sqllocaldb+delete+v11.0|301788|在那之后，一切都恢复正常(+LocalDB处理的所有其他数据库也都消失了！)|301789|编辑:这不是真的。我刚试过，v11.0会自动重新创建，并且所有mdfs都保持可用。我还没有尝试过使用“非基于文件的”LocalDB。|301790|令人困惑的是，如果其他地方出了问题，我也会得到这个错误。因此，我的建议是，如果你想确保你的数据库设置是可靠的:从头开始创建一个新的解决方案/项目，使用最基本的数据库命令(添加实体，显示所有实体，删除所有实体)，看看它是否有效。|301791|如果是，那么问题出在VS2013配置和版本控制以及nuget之类的深渊中。|301792|如果不是，则说明您的LocalDB安装有问题。|301793|对于任何真正想要了解EF中发生了什么的人(我仍然不确定我是否想了解:-)+http://odetocode.com/Blogs/scott/archive/2012/08/14/a-troubleshooting-guide-for-entity-framework-connections-amp-migrations.aspx|offset|length|301794|附言:如果您需要运行示例项目，请轻推我。|301795|entityMap|0|LINK|mutability|MUTABLE|url|http://odetocode.com/Blogs/scott/archive/2012/08/14/a-troubleshooting-guide-for-entity-framework-connections-amp-migrations.aspx^0|0|0|0|0|0|0|0|0|0|0|0|11|3K|0|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1D|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1E|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|1F|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|1G|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|1H|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|1I|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1J|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1K|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1L|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1M|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1N|8|@]|9|@$10|1O|11|1P|1|1Q]]|A|$]]|$1|12|3|13|5|6|7|1R|8|@]|9|@]|A|$]]|$1|14|3|-4|5|6|7|1S|8|@]|9|@]|A|$]]]|15|$16|$5|17|18|19|A|$1A|1B]]]]

I had the same error.
Weird thing was, I had one new project form scratch, there it worked perfectly and another, much bigger project, where I always ran into that error message.

The perfecrtly working project (nearly) always creates the database (indluding the files) automatically. It can be any command, read, write, update. The files get created.
Of course it uses

<pre><code>DropCreateDatabaseIfModelChanges
</code></pre>

There is only one case, when it gets troubled: IF the mdf is auto-created and you delete the mdf and log file. Then that was about it. Say good-bye to your autocreation...

The only way I found to fix it was like mentioned:

<pre><code>sqllocaldb stop v11.0 &amp; sqllocaldb delete v11.0
</code></pre>

After that, everything is back to normal (and all other Databases handled by LocalDB also gone!).

EDIT: That was not true. I just tried it and the v11.0 gets automatically recreated and all mdfs stay available. I have not tried with "non file based" LocalDBs.

The confusing thing is, I also got this error if something else was wrong.
So my suggestion is, if you want to make sure your DB-Setup is sound and solid:
Create a new solution/project from scratch, use the most basic DB commands (Add an entity, show all entities, delete all entities) and see if it works. 

If YES, the problem is somewhere in the abyss of VS2013 config and versioning and nuget and stuff.

IF NO, you have a problem with your LocalDB installation.

For anyone who really wants to understand what's going on in EF (and I am still not sure if I do :-) )
<a href="http://odetocode.com/Blogs/scott/archive/2012/08/14/a-troubleshooting-guide-for-entity-framework-connections-amp-migrations.aspx" rel="nofollow">http://odetocode.com/Blogs/scott/archive/2012/08/14/a-troubleshooting-guide-for-entity-framework-connections-amp-migrations.aspx</a>

P.S.: Nudge me if you need the running example project.

blocks|key|301832|text|奇怪的是，对于完全相同的问题，帮助我的是将配置的下一部分中的‘改为'v11.0’。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|301833|<defaultConnectionFactory+type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory,+EntityFramework">
++++++<parameters>
++++++++<parameter+value="v11.0"+/>
++++++</parameters>|code-block|syntax|javascript|301834|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Strangely, for the exact same issue, what helped me was changing the ' to 'v11.0' in the following section of the config.

<pre><code>&lt;defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework"&gt;
 &lt;parameters&gt;
 &lt;parameter value="v11.0" /&gt;
 &lt;/parameters&gt;
</code></pre>

blocks|key|84393|text|我最近遇到了同样的问题。这里有一件事需要检查。在visual+studio中，有三个地方我们应该检查和删除数据库。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|84394|1.+Solution+Explorer's+App_Data+folder
2.+Server+Explorer's+Data+Connection+menu
3.+SQL+Server+Object+Explorer|code-block|syntax|javascript|84395|当我从前两个点删除数据库时，错误仍然发生。因此，我还需要从SQL+Server对象资源管理器中删除该数据库。这样我就可以很容易地运行“update-database”命令而不会出错。希望这能有所帮助。|84396|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I recently ran into the same problem. Here is one thing to check. 
in visual studio there are three place we should check and remove the database. 

<pre><code>1. Solution Explorer's App_Data folder
2. Server Explorer's Data Connection menu
3. SQL Server Object Explorer
</code></pre>

When I delete database from the first two point, the error still occurs. So, I needed to delete the database from the SQL Server Object Explorer as well. 
Then I could easily run the 'update-database' command without error. 
Hope this helps.

blocks|key|301919|text|我发现注释掉用于初始化数据库的上下文部分解决了这个问题。我还没有时间找出种子语句的错误，但删除种子语句解决了问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|301920|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I found that commenting out the context section used to initialise the database resolved the problem. Havnt had time to find out what was wrong with the seeding statements yet, but removing the seeding resolved the problem.

blocks|key|84453|text|您已经在服务器资源管理器中安装了该数据库的旧副本。因此，这是服务器对象资源管理器/+SQL服务器中的一个简单的命名冲突。在决定将其移动到Apps_Data文件夹之前，您可能已经创建了相同的数据库目录名称。因此该数据库名称已经存在，只需删除即可。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|84454|只需进入Visual+Studio+>+View+>+SQL+Server+Object+Explorer并删除旧的数据库名称及其连接即可。再次重试您的应用程序，它应该会在App_Data中安装.mdf文件，并在服务器资源管理器中再次创建完全相同的数据库。|84455|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

You already have an old copy of that database installed in Server Explorer. So its a simple naming collision in the Server Object Explorer / SQL server. You likely created the same database Catalog Name already before you decided to move it to the Apps_Data folder. So that Database name already exists and just needs to be deleted.

Just go into Visual Studio > View > SQL Server Object Explorer and delete the old database name and its connection. Retry your app again and it should install the .mdf file in App_Data and create the same exact database again in the Server Explorer.

blocks|key|84478|text|在阅读“MicrosoftMVC5入门%7C+ASP.NET文档”教程时，我也遇到了同样的错误。我在Visual+Studio+2015上。我打开视图->+SQL+Server对象资源管理器，删除了以教程命名的数据库，然后它就可以工作了。请参阅Delete+.mdf+file+from+app_data+causes+exception+cannot+attach+the+file+as+database|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|84479|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/13001441/delete-mdf-file-from-app-data-causes-exception-cannot-attach-the-file-as-databa^0|3C|2A|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

I had the same error while following the tutorial on "Getting Started with ASP.NET MVC 5 | Microsoft Docs". I was on Visual Studio 2015.
I opened View-> SQL Server Object Explorer and deleted the database named after the tutorial, then it could work.
see <a href="https://stackoverflow.com/questions/13001441/delete-mdf-file-from-app-data-causes-exception-cannot-attach-the-file-as-databa">Delete .mdf file from app_data causes exception cannot attach the file as database</a>

blocks|key|301989|text|我们在使用ASP.Net+Core2.1运行dotnet+ef+database+update时就遇到了这个问题；看起来AttachDbFileName不支持相对路径。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|301990|System.Data.SqlClient.SqlException+(0x80131904):+Cannot+attach+the+file+'.\OurDbName.mdf'+as+database+'OurDbName'.|301991|只是想在这里向其他可能遇到这个问题的人表达一下。“修复”是使用绝对路径。|301992|另请参阅：https://github.com/aspnet/EntityFrameworkCore/pull/6446|301993|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/aspnet/EntityFrameworkCore/pull/6446^0|M|P|1O|G|0|0|36|0|0|5|1J|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|11|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|12|8|@]|D|@$9|13|A|14|1|15]]|E|$]]|$1|L|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|M|$N|$5|O|P|Q|E|$R|S]]]]

We just ran into this ourselves when running <code>dotnet ef database update</code> using ASP.Net Core 2.1; looks like relative paths aren't supported with <code>AttachDbFileName</code>. 

<code>System.Data.SqlClient.SqlException (0x80131904): Cannot attach the file '.\OurDbName.mdf' as database 'OurDbName'.
</code>

Just wanted to express that here for other people who might be bumping into this. The "fix" is use absolute paths.

See also: <a href="https://github.com/aspnet/EntityFrameworkCore/pull/6446" rel="nofollow noreferrer">https://github.com/aspnet/EntityFrameworkCore/pull/6446</a>

blocks|key|302015|text|遇到了这个问题。在我的例子中，是因为在iispexress仍在运行时删除了.mdf，因此仍在使用DB。右键单击系统托盘中的iisexpress，然后单击退出，然后删除MDF以防止此错误实际发生。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|302016|要修复此错误，只需在VS中右键单击App-Data文件夹add+new+item+>+SQL+Server+Database即可。名称:使用update-database错误提供的数据库名称，单击Add。|302017|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Ran into this issue. Caused in my case by deleting the .mdf while iispexress was still running and therefor still using the DB.
Right click on iisexpress in system tray and click exit THEN delete the MDF to prevent this error from actually occurring.

To fix this error simply within VS right click the App-Data folder add new item > SQL Server Database. Name: [use the database name provided by the update-database error]
Click Add.

blocks|key|302052|text|如果你碰巧已经应用了迁移，这可能会修复它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|302053|转到您的Web.config并根据迁移文件更新您的连接字符串。|302054|Data+Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=%7CDataDirectory%7C\aspnet-GigHub-201802102244201.mdf;Initial+Catalog=aspnet-GigHub-201802102244201;|code-block|syntax|javascript|302055|日期字符串应与迁移时的第一个数字匹配。|302056|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you happen to apply migrations already this may fix it.

Go to your Web.config and update your connection string based on your migration files.

<pre><code>Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\aspnet-GigHub-201802102244201.mdf;Initial Catalog=aspnet-GigHub-201802102244201;
</code></pre>

The datestrings should match the first numbers on your Migrations.

blocks|key|84609|text|遇到类似的问题并不完全相同，一个数据库已经存在的案例通过以下代码解决了这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|84610|​|84611|<add+name="DefaultConnection"+connectionString="Data+Source=.;AttachDbFilename=%7CDataDirectory%7C\aspnet-EjournalParsing-20180925054839.mdf;Initial+Catalog=aspnet-EjournalParsing-20180925054839;Integrated+Security=True"
++++++providerName="System.Data.SqlClient"+/>|code-block|syntax|javascript|84612|84613|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|N|8|@]|9|@]|A|$G|H]]|$1|I|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|K|$]]

Ran into the similar problem not exactly the same, A case of Database already existed the issue was solved by following code.

<div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;add name="DefaultConnection" connectionString="Data Source=.;AttachDbFilename=|DataDirectory|\aspnet-EjournalParsing-20180925054839.mdf;Initial Catalog=aspnet-EjournalParsing-20180925054839;Integrated Security=True"
 providerName="System.Data.SqlClient" /&gt;</code></pre>
</div>
</div>

blocks|key|302096|text|在我的例子中，从连接字符串中删除Initial+Catalog=....解决了这个问题|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|302097|entityMap^0|G|K|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

In my case removing <code>Initial Catalog=....</code> from connection string resolved the issue

blocks|key|302114|text|我没有读取所有的响应，但是如果您的.mdf文件不是C:\Temp安装路径的一部分，那么SQL数据库引擎服务帐户将没有创建和写入.ldf文件的权限，甚至没有读取.mdf文件的权限。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|302115|解决方案是，您必须将文件系统权限授予运行SQL实例服务的SQL+Server数据库引擎服务帐户。因此，对于我来说，我通过Windows+Explorer授予了对我的C:\Temp路径的完全控制权限，该路径包含了我的NT+Service\MSSQL$SQLEXPRESS01和NT+Service\MSSQL$MSSQL2016帐户的.mdf文件。|302116|这里有一个详细说明这个问题的Microsoft+article。|302117|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/configure-file-system-permissions-for-database-engine-access?view=sql-server-ver15^0|H|4|P|7|1R|4|27|4|0|2A|7|2Z|T|3T|Q|4M|4|0|E|H|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|19|8|@]|D|@$9|1A|A|1B|1|1C]]|E|$]]|$1|J|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]]]

I didn't read all the responses, but if your <code>.mdf</code> file is NOT part of the SQL installation path, like <code>C:\Temp</code>, then the SQL Database Engine service account(s) will not have permission to create and write to the <code>.ldf</code> file or even read the <code>.mdf</code> file.

The solution is you have to give file system permissions to the SQL Server database engine service account that runs the SQL instance service. So for me, I gave permissions full control via Windows Explorer to my <code>C:\Temp</code> path that contained my <code>.mdf</code> file for the <code>NT Service\MSSQL$SQLEXPRESS01</code> and <code>NT Service\MSSQL$MSSQL2016</code> accounts.

Here is a <a href="https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/configure-file-system-permissions-for-database-engine-access?view=sql-server-ver15" rel="nofollow noreferrer">Microsoft article</a> that details this very issue.

Basically I've followed a tutorial and decided to delete the <code>.mdf</code> file afterwards.

Now whenever I try to run the application I get the following error (the title of this thread).
The code where I get the error is shown below (ASP.NET MVC 4):

<pre><code>OdeToFoodDB db = new OdeToFoodDB();

public ActionResult Index()
{
 var model = db.Restaurants.ToList();
 return View(model);
}
</code></pre>

My connection string is the following:

<pre><code>&lt;add name="DefaultConnection" 
 connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=OdeToFoodDb;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\OdeToFoodDb.mdf" 
 providerName="System.Data.SqlClient" /&gt;
</code></pre>

I've tried looking at the SQL Server Object Explorer but it looks the following:

Also, in Server Explorer I don't see any data connections.

And when I try to add a new connection in Server Explorer I don't see any databases named <code>OdeToFoodDb</code>.

Sorry for this wide question but I'm new to Entity Framework and don't quite get what's wrong here.

Cannot attach the file *.mdf as database

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基本上，我遵循了一个教程，然后决定删除.mdf文件。现在，每当我尝试运行应用程序时，我都会得到以下错误(此线程的标题)。我得到错误的代码如下所示(ASP.NET mvc4)：OdeToFoodDB db = new OdeToFoodDB();public ActionResult Index(){    var mo...

问无法将文件*.mdf附加为数据库
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