[英]WPF Core - Connection Strings inside App.config Not Working
在面对上述问题时,甚至遵循了连接字符串 - EF Core 中的简单演练,但发现在将连接字符串硬编码为:
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Blogging;Trusted_Connection=True;");
}
使用推荐的方法插入 App.config 文件,如:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<connectionStrings>
<add name="BloggingDatabase"
connectionString="Server=(localdb)\mssqllocaldb;Database=Blogging;Trusted_Connection=True;" providerName="System.Data.SqlClient" />
</connectionStrings>
</configuration>
并将主要代码更新为:
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer(ConfigurationManager.ConnectionStrings["BloggingDatabase"].ConnectionString);
}
不成功,并且在执行迁移时遇到以下错误:
System.NullReferenceException: Object reference not set to an instance of an object.
at Intro.BloggingContext.OnConfiguring(DbContextOptionsBuilder optionsBuilder) in C:\<...FileLocation...>\AppDbContext.cs:line 14
at Microsoft.EntityFrameworkCore.DbContext.get_InternalServiceProvider()
at Microsoft.EntityFrameworkCore.DbContext.Microsoft.EntityFrameworkCore.Infrastructure.IInfrastructure<System.IServiceProvider>.get_Instance()
at Microsoft.EntityFrameworkCore.Infrastructure.Internal.InfrastructureExtensions.GetService[TService](IInfrastructure`1 accessor)
at Microsoft.EntityFrameworkCore.Infrastructure.AccessorExtensions.GetService[TService](IInfrastructure`1 accessor)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>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)
Object reference not set to an instance of an object.
背后的原因可能是什么?
预先感谢您的审阅和回复。
终于在这里找到了唯一满意的镜像问题答案。
App.Config 不是WPF Core 的连接字符串的正确选择。 在这方面,它是一个足够成功的 appsettings.json 文件。
奇怪的!!! 使用索引技术时,例如: optionsBuilder.UseSqlServer(System.Configuration.ConfigurationManager.ConnectionStrings[0].ConnectionString); 成功了! – Faraz Ahmed Qureshi 3 月 28 日 17:06
这确实有效
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