如何在Startup.cs之外设置数据库连接字符串用户名和密码？

Question

I want to be able to restrict CRUD access for non-logged in users of a web application. This means I need to set the connection string after I have validated if they are a currently logged in user or not.

I have CRUD restrictions in my code, but want to put the account permissions in place to ensure users cannot access tables they are not supposed to access, or perform actions they are not supposed to perform.

Right now my connection string is set in my Startup.cs file:

services.AddDbContext<WorldContext>(options => options
    .UseMySql(_config["ConnectionStrings:Database"]));

How can I set the connection string, or at least the username & password for the DB account outside of startup? Sometime after I have validated that the user is logged in?

I am using ASP.Net Core , Entity Framework Core , and Asp.NET Core Identity .

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I want to grant only the necessary permissions that the user will need. As quoted from here: https://msdn.microsoft.com/en-us/library/cc716760(v=vs.110).aspx

Grant users only the necessary permissions in the data source. A data source administrator should grant only the necessary permissions to users. Even though Entity SQL does not support DML statements that modify data, such as INSERT, UPDATE, or DELETE, users can still access the connection to the data source. A malicious user could use this connection to execute DML statements in the native language of the data source.

Answer 1

There are multiple ways to do this but I would like to do it like this.

Create two DbContext one for user authentications and reading users database login details. Second for users which used to do CRUD operations on rest of the tables.

Question is how we register these two DbContext and where???

Here Asp.net Core Dependence Injection will did lots of work for us.

We can register the LoginDbContext in Startup.cs (as sample project did) which will used to validate the users and get there DB users login details.Also need to Inject IServiceCollection where we validate the users, So we can register the CRUDDbContext while creating connection string with user detail which we get from database. After that we can Inject the CRUDDbContext in controller or repository classes.