Connection string in asp.net core

ASP.NET Core

In ASP.NET Core the configuration system is very flexible, and the connection string could be stored in appsettings.json, an environment variable, the user secret store, or another configuration source. See the Configuration section of the ASP.NET Core documentation for more details.

For instance, you can use the Secret Manager tool to store your database password and then, in scaffolding, use a connection string that simply consists of Name=.

dotnet user-secrets set ConnectionStrings:YourDatabaseAlias "Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=YourDatabase"
dotnet ef dbcontext scaffold Name=ConnectionStrings:YourDatabaseAlias Microsoft.EntityFrameworkCore.SqlServer

Or the following example shows the connection string stored in appsettings.json.

{
  "ConnectionStrings": {
    "BloggingDatabase": "Server=(localdb)\\mssqllocaldb;Database=EFGetStarted.ConsoleApp.NewDb;Trusted_Connection=True;"
  },
}

Then the context is typically configured in Startup.cs with the connection string being read from configuration. Note the GetConnectionString() method looks for a configuration value whose key is ConnectionStrings:. You need to import the Microsoft.Extensions.Configuration namespace to use this extension method.

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext(options =>
        options.UseSqlServer(Configuration.GetConnectionString("BloggingDatabase")));
}

Hi Naresh,

You can explain a bit more about your question? As a simple answer Connection string is an exact replacement of Web config ( Old ASP.NET Projects ).

Reference :

https://stackoverflow.com/questions/68980778/config-connection-string-in-net-core-6

https://www.c-sharpcorner.com/Blogs/database-connections-in-asp-net-core-20

In ASP.NET Core the configuration system is very flexible, and the connection string could be stored in appsettings.json, an environment variable, the user secret store, or another configuration source. 

In appsettings.json

{
  "ConnectionStrings": {
    "BloggingDatabase": "Server=(localdb)\\mssqllocaldb;Database=EFGetStarted.ConsoleApp.NewDb;Trusted_Connection=True;"
  },
}

Then the context is typically configured in Startup.cs with the connection string being read from configuration. Note the GetConnectionString() method looks for a configuration value whose key is ConnectionStrings:. You need to import the Microsoft.Extensions.Configuration namespace to use this extension method.

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext(options =>
        options.UseSqlServer(Configuration.GetConnectionString("BloggingDatabase")));
}

for more details please refer below link

https://learn.microsoft.com/en-us/ef/core/miscellaneous/connection-strings