Entity Framework Core 7执行Scaffold-DbContext时触发空引用异常

问题场景 #

执行以下PowerShell命令通过EF Core 7反向生成数据库模型：

Scaffold-DbContext -connection name=constring Microsoft.EntityFrameworkCore.SqlServer -Output Models

appsettings.json中的连接字符串配置：

"ConnectionStrings": {
    "constring": "Server=.\\SQLExpress;Database=Words;Trusted_Connection=True; TrustServerCertificate=True"
}

命令执行后编译成功，但抛出NullReferenceException错误：

System.NullReferenceException: Object reference not set to an instance of an object.

   at Microsoft.EntityFrameworkCore.Scaffolding.Internal.CSharpDbContextGenerator.TransformText()  
   at Microsoft.EntityFrameworkCore.Scaffolding.Internal.CSharpModelGenerator.ProcessTemplate(ITextTransformation transformation)
   at Microsoft.EntityFrameworkCore.Scaffolding.Internal.CSharpModelGenerator.GenerateModel(IModel model, ModelCodeGenerationOptions options)
   at Microsoft.EntityFrameworkCore.Scaffolding.Internal.ReverseEngineerScaffolder.ScaffoldModel(String connectionString, DatabaseModelFactoryOptions databaseOptions, ModelReverseEngineerOptions modelOptions, ModelCodeGenerationOptions codeOptions)
   at Microsoft.EntityFrameworkCore.Design.Internal.DatabaseOperations.ScaffoldContext(String provider, String connectionString, String outputDir, String outputContextDir, String dbContextClassName, IEnumerable`1 schemas, IEnumerable`1 tables, String modelNamespace, String contextNamespace, Boolean useDataAnnotations, Boolean overwriteFiles, Boolean useDatabaseNames, Boolean suppressOnConfiguring, Boolean noPluralize)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.ScaffoldContextImpl(String provider, String connectionString, String outputDir, String outputDbContextDir, String dbContextClassName, IEnumerable`1 schemaFilters, IEnumerable`1 tableFilters, String modelNamespace, String contextNamespace, Boolean useDataAnnotations, Boolean overwriteFiles, Boolean useDatabaseNames, Boolean suppressOnConfiguring, Boolean noPluralize)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.ScaffoldContext.<>c__DisplayClass0_0.<.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)

补充说明 #

明确EF Core并非数据库，本次操作也不是导入数据（另有应用负责数据导入）。

解决步骤 #

通过以下步骤解决了该问题：

• 修改实体类定义
• 删除数据库中的目标表
• 清除所有旧的迁移文件及记录
• 使用dotnet CLI执行新迁移并更新数据库

内容的提问来源于stack exchange，提问作者user2049142