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.net-core - 如何为现有 AzureCosmosDB 生成模型类？

问题描述

我有一个包含所有数据和集合的现有 Azure CosmosDB。现在我正在寻找基于我为 SQLServer 数据库所做的相同过程生成模型类。

https://www.learnentityframeworkcore.com/walkthroughs/existing-database

我使用导航到包含解决方案文件的文件夹的 cmd 实用程序尝试了以下命令：

dotnet ef dbcontext scaffold <Azure CosmosDB ConnectionString> Microsoft.EntityFrameworkCore.Cosmos -o Models

在执行上述命令时，我收到以下错误：

System.InvalidOperationException: Unable to find expected assembly attribute named DesignTimeProviderServicesAttribute in provider assembly Microsoft.EntityFrameworkCore.Cosmos. This attribute is required to identify the class which acts as the design-time service provider factory.
   at Microsoft.EntityFrameworkCore.Design.Internal.DesignTimeServicesBuilder.ConfigureProviderServices(String provider, IServiceCollection services, Boolean throwOnError)
   at Microsoft.EntityFrameworkCore.Design.Internal.DesignTimeServicesBuilder.Build(String provider)
   at Microsoft.EntityFrameworkCore.Design.Internal.DatabaseOperations.ScaffoldContext(String provider, String connectionString, String outputDir, String outputContextDir, String dbContextClassName, IEnumerable`1 schemas, IEnumerable`1 tables, Boolean useDataAnnotations, Boolean overwriteFiles, Boolean useDatabaseNames)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.ScaffoldContextImpl(String provider, String connectionString, String outputDir, String outputDbContextDir, String dbContextClassName, IEnumerable`1 schemaFilters, IEnumerable`1 tableFilters, Boolean useDataAnnotations, Boolean overwriteFiles, Boolean useDatabaseNames)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.ScaffoldContext.<>c__DisplayClass0_1.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Unable to find expected assembly attribute named DesignTimeProviderServicesAttribute in provider assembly Microsoft.EntityFrameworkCore.Cosmos. This attribute is required to identify the class which acts as the design-time service provider factory.

谁能帮我知道如何解决这个问题？

标签： .net-coreazure-cosmosdb

解决方案

为了使其工作，数据库提供程序需要包含有关如何进行脚手架的信息。目前，CosmosDB 不支持此功能，因此您将无法使用 CLI 从现有数据库创建模型。

有一个Github 问题开放以改进错误消息以使其更清晰。如果您愿意，可以在该存储库上打开一个问题，请求为 Cosmos 添加该功能。

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