How do I connect ASP.NET Container to Postgres container?

Question

Problem

I have an API in asp.net core and I'm using Npgsql with it which is running on docker. When I'm running it on visual studio with swagger it works, but if i'll put my api into container it can't connect to the postgres.

The problem comes up when I send a request to an endpoint.

What have I tried?

I've checked most of the posts. I think its related with my connection string. I've tried everything. any of the ip adresses nor the container names worked out.

Configs

Here is my appsettings.json in asp

"ConnectionStrings": {
"PostgresDatabase": "Host=local_pgdb;Port=5432; Database=postgres; Username=user; Password=admin;MultipleActiveResultSets=true"
  },

here are my docker files.

postgres docker file

    version: "3.8"
services:
  db:
    image: postgres
    container_name: local_pgdb
    restart: always
    ports:
      - "5432:5432"
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: admin
    volumes:
      - local_pgdata:/var/lib/postgresql/data
  pgadmin:
    image: dpage/pgadmin4
    container_name: pgadmin4_container
    restart: always
    ports:
      - "5050:80"
    environment:
      PGADMIN_DEFAULT_EMAIL: [email protected]
      PGADMIN_DEFAULT_PASSWORD: admin
    volumes:
      - pgadmin-data:/var/lib/pgadmin

volumes:
  local_pgdata:
  pgadmin-data:

asp api dockerfile

    FROM mcr.microsoft.com/dotnet/aspnet:7.0 AS base
WORKDIR /app
ENV ASPNETCORE_ENVIRONMENT Development
ENV ASPNETCORE_URLS=http://+:80 

FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build
WORKDIR /src
COPY ["haymatlosApi.csproj", "."]
RUN dotnet dev-certs https
RUN dotnet restore "./haymatlosApi.csproj"
COPY . .
WORKDIR "/src/."
RUN dotnet build "haymatlosApi.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "haymatlosApi.csproj" -c Release -o /app/publish /p:UseAppHost=false

FROM base AS final
WORKDIR /app
EXPOSE 80/tcp
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "haymatlosApi.dll"]

Problem in the cmi in docker.

warn: Microsoft.AspNetCore.HttpsPolicy.HttpsRedirectionMiddleware[3]
2023-08-23 17:45:53       Failed to determine the https port for redirect.
2023-08-23 17:45:55 warn: Microsoft.EntityFrameworkCore.Query[10102]
2023-08-23 17:45:55       The query uses a row limiting operator ('Skip'/'Take') without an 'OrderBy' operator. This may lead to unpredictable results. If the 'Distinct' operator is used after 'OrderBy', then make sure to use the 'OrderBy' operator after 'Distinct' as the ordering would otherwise get erased.
2023-08-23 17:45:55 warn: Microsoft.EntityFrameworkCore.Query[10102]
2023-08-23 17:45:55       The query uses a row limiting operator ('Skip'/'Take') without an 'OrderBy' operator. This may lead to unpredictable results. If the 'Distinct' operator is used after 'OrderBy', then make sure to use the 'OrderBy' operator after 'Distinct' as the ordering would otherwise get erased.
        enter code herefail: Microsoft.EntityFrameworkCore.Database.Connection[20004]
    2023-08-23 16:56:31       An error occurred using the connection to database 'postgres' on server ''.
    2023-08-23 16:56:31 fail: Microsoft.EntityFrameworkCore.Query[10100]
    2023-08-23 16:56:31       An exception occurred while iterating over the results of a query for context type 'haymatlosApi.haymatlosApi.Models.PostgresContext'.
    2023-08-23 16:56:31       System.InvalidOperationException: An exception has been raised that is likely due to a transient failure.
    2023-08-23 16:56:31        ---> Npgsql.NpgsqlException (0x80004005): Failed to connect to [::1]:5432
    2023-08-23 16:56:31        ---> System.Net.Sockets.SocketException (99): Cannot assign requested address