When the .NET Entity Framework retrieves data from the database and parses it into the structure that we specify in our code, we have to make sure nullable columns are modeled with nullable properties in our code.
When null values are retrieved and the structure in the code does not allow null value in any property, we get the System.Data.SqlTypes.SqlNullValueException exception
Data is Null. This method or property cannot be called on Null values.
Make sure all nullable columns are modeled with nullable properties.
CREATE TABLE [dbo].[task](
[id] [int] IDENTITY(1,1) NOT NULL,
[filenames] [nvarchar](max) NULL,
[source_path] [nvarchar](255) NULL,
[target_path] [nvarchar](255) NULL
public class task
{
public int id { get; set; }
public string? filenames { get; set; }
public string? source_path { get; set; }
public string? target_path { get; set; }
}
Standalone Windows executables are compiled ahead of time (AOT) and distributed as three executable files (.exe, .dll, .runtimeconfig.json). This format is ideal for small executables called from the command line or from other applications.
To create an AOT Windows executable in Visual Studio 2022 or later
Start a new project
Create a C# console app
Name the app
Select .NET 8.0 or later framework, and Enable native AOT publish
To test the application we will write some temporary code in Program.cs
// See https://aka.ms/new-console-template for more information
Console.WriteLine("Test executable started");
// Read the command line arguments into an array
string[] arguments = args;
Console.WriteLine($"Number of command line arguments {arguments.Length}");
if (arguments != null && arguments.Length > 0)
{
var firstArgument = arguments[0];
Console.WriteLine($"First argument = {firstArgument}");
if (firstArgument == "ERROR" )
{
Console.WriteLine("Throw divide by zero exception");
int a = 0;
int b = 1 / a;
}
}
Console.WriteLine("Test executable exited without error");
Build the executable
Prerequisites
To be able to build, link and publish the standalone executable we need to install the “Desktop development with C++” Visual Studio workload.
In the Tools menu select Get Tools and Features
Install the Desktop development with C++ workload
Publish the executable
In the Solution Explorer right-click the project and select Publish
Select Folder as the target
Select Folder again for the specific target
Select the target location and click Finish
Close the dialog when the build has been completed
Running the standalone executable
By default the output is placed in the bin\Debug\net8.0 directory
To run the (not really) “standalone” application, we need the following three files in the same directory:
In this post we will develop a .NET 8 console application which reads the configuration values from environment variables. This enables us deploy the application in an EKS cluster and read the config values from any secure secret storage.
The develoment environment
Docker configuration
To prevent Visual Studio from debugging in Docker containers
Debugging in Docker containers provides a stable, production like environment for your application, but larger applications can take a long time to build into containers. To stop Visual Studio debugging in Docker containers see Prevent Visual Studio 2022 from debugging in Docker. Official documentation is at Project warmup.
To allow Visual Studio to debug in Docker containers
If you want to debug in Docker containers to see how your application will run in production
Enable Docker Desktop execution
To be able to start Docker Desktop on Windows your user id has to be in the docker-users local user group. To add your user to the group
Open a command prompt as Administrator
Get the username:
whoami
Add the user to the docker-users user group:
net localgroup docker-users "your-user-id" /ADD
Log out and log in into Windows for the change to take effect.
Enable WSL (Windows Subsystem for Linux) for better performance with Docker Desktop
If Docker Desktop recommends using WSL instead of Hyper-V and WSL is not installed on your computer
Open an Administrator PowerShell window and execute
Start Visual Studio 2022 community edition or newer
Create a new Console application using the C# programming language
Create the git repository
IMPORTANT!!! To exclude the .env file and other temporary and build files from the Git commit create the .gitignore file
Open a terminal in the root directory of the repository and execute the commands
Create the .gitignore file
dotnet new gitignore
Create the Git repository
git init
Read the environment variables
Environment variables are the safest and most flexible way to store sensitive configuration values. This way those are never committed to source control.
Install the NuGet packages
To be able to access environment variables we need to install the following NuGet packages
Microsoft.Extensions.Configuration.EnvironmentVariables – to read environment variables
DotNetEnv – to load environment variables from .env files on the developer workstation
To install the packages from the command line, open a terminal in the project directory and execute
Create the .env file in the solution directory and add a key value pair
ENVIRONMENT=local
Write the code
Create the Settings.cs class to store the configuration values
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace MY_NAMESPACE
{
internal class Settings
{
public string? Environment { get; set; }
public string? AppName { get; set; }
}
public class ConnectionStrings
{
public string? SQLServer { get; set; }
}
}
Create the Configuration.cs class to read the configuration values form the environment variables
using DotNetEnv;
using Microsoft.Extensions.Configuration;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace MY_NAMESPACE
{
internal class Configuration
{
/// <summary>
/// Reads the config values from the environment variables and returns the Settings object
/// </summary>
/// <returns></returns>
public static Settings BuildAppSettings()
{
// Try to load the environment variables from the .env file for local development
// Place the .env file in the root folder of the solution
DotNetEnv.Env.TraversePath().Load();
// Read the environment variables
var environmentConfiguration = new ConfigurationBuilder()
.AddEnvironmentVariables().Build();
// Instantiate and populate the Settings object
var settings = new Settings()
{
Environment = environmentConfiguration["ENVIRONMENT"],
AppName = environmentConfiguration["APPNAME"]
};
// Return the Settings object
return settings;
}
}
}
In the Program.cs file call Configuration to load the Settings object from the environment variables.
// See https://aka.ms/new-console-template for more information
using MY_APPLICATION;
using DotNetEnv;
using Microsoft.Extensions.Configuration;
// args is a string array that contains the command line arguments
string[] arguments = args;
Console.WriteLine($"Number of command line arguments {arguments.Length}");
// Read the configuration values
Settings settings = Configuration.BuildAppSettings();
Console.WriteLine($"Envronment: {settings.Environment}");
Console.WriteLine($"AppName: {settings.AppName}");
Visual Studio Community Edition has all the features for MSSQL SSIS package development. We need to download the SQL Server Integration Services Projects extension.
In the package properties set DelayValidation to True to avoid long wait when opening the package.
When we try to refresh or install NPM packages there can be version conflicts between packages and the dependency requirements. The error message can vary, but it is similar to
npm error code ERESOLVE npm error ERESOLVE could not resolve
To be able to install or refresh NPM packages
Delete the package-lock.json file
Delete the node_modules directory
Execute the npm install [MY_PACKAGE_NAME] commands one-by-one
These steps will most likely successfully reinstall the NPM packages, and if there is a conflict it will show in the response.
React Router, written by the Remix team, provides the missing routing services for React applications, used by 7 million websites. Remix propvides other features to make react application development more intuitive by providing
Automatic code splitting
Simplified data loading
Form Actions, Server actions
Simplified pending states
Optimistic UI
Server rendering
Static pre-rendering
React Server Components – RSC (coming soon)
The Remix team also added Vite, as it “has risen substantially in popularity, offering a fast dev experience, optimized builds, and a rich plugin ecosystem and authoring experience.”
As Upgrading from Remix to React Router states “React Router v7 is the next major version of Remix after v2”. React Router v7 now contains the functionality of @remix-run/node, @remix-run/cloudflare, etc.
The blog, Merging Remix and React Router explains the Remix team’s decisions, and give you the reason to make the change.
To upgrade from Remix to React Router 7
Upgrade Node to version 20
React Router v7 requires Node.js version 20 or higher, so at the time of writing most users have to upgrade Node.js.
If you used Homebrew to install Node.js, execute the commands
brew update # Update Homebrew
brew tap --repair # If brew notifies you about broken references
brew upgrade # If there are "Outdated Formulae"
brew upgrade node # Update Node.js to the latest stable version
Create a new Remix site using the React Router framework
At the time of writing these are the recommended steps:
Create the base application
npx create-react-router@latest MY_APP_NAME
If you want to keep your application in a subdirectory of your repository, select No for “Initialize a new git repository?”. Select Yes for “Install dependencies with npm?”
The process will create a folder matching the name of the application you specify, and will add that name to the package.json file as the “name” element.
The .gitignore file, and the .git directory will be placed in the application directory. As an application repository usually contains more than just the web application, like Terraform scripts, documentation, move the .gitignore file higher, remove the .git directory and recreate the repository with the git init command in the top level directory of your application. We also need to update the .gitignore file, and remove the leading slashes from all lines, as the node_modules, .react-router, and build directories are not in the root directory anymore.
Make sure at least the “Secrets” section is in the the top level .gitignore file to avoid committing secrets into Git.
Unused imports will trigger unnecessary error messages during the migration. To remove unused imports
In Visual Studio Code hover above an unused import
Click Quick Fix
Select Delete all unused imports
Remove imports
Remove these imports and if indicated import from a new module
Import
From
To
LoaderArgs
react-router
ActionArgs
react-router
json
react-router
Route
“./+types/home”
“./+types/root”
Replace some lines
Use any instead of LoaderArgs and ActionArgs in the Loader and Action function signature. Use data instead of json to return values from the Loader to the client. Import data from react-router
- export async function loader({ request }: LoaderArgs) {
+ export async function loader({ request }: any) {
- export async function action({ request }: ActionArgs) {
+ export async function action({ request }: any) {
- return json({
+ return data({
also add import { data } from "react-router";
Update your Make file
If you maintain a Makefile with the list of modules you need to install to make the application work, these modules are installed by React-Router during the application generation
install:
npm i @react-router/node
npm i @react-router/serve
npm i isbot
npm i react
npm i react-dom
npm i react-router
npm -D @react-router/dev
npm -D @tailwindcss/vite
npm -D @types/node
npm -D @types/react
npm -D @types/react-dom
npm -D react-router-devtools
npm -D tailwindcss
npm -D typescript
npm -D vite
npm -D vite-tsconfig-paths
Update the routing
Edit the app/routes.ts file and set the path for the index to point to your home page. Add all routing to this file.
import { type RouteConfig, index, route } from "@react-router/dev/routes";
export default [
index("routes/_index.tsx"),
route("data_editor", "routes/data_editor.tsx")
route("us/user_editor", "routes/us.user_editor.tsx")
] satisfies RouteConfig;
Run the application
Start the server with the npm run dev command. See Troubleshooting below for the most common error messages.
Install the missing modules
As you refresh the page, the Cannot find module ‘…’ imported from ‘…’ message will let you know which modules need to be installed with the npm install … command. Update the install section of your Makefile to keep the list of necessary modules.
Separate files for server side and client side functions
To make the application work using the new framework and the Vite development tools, we have to make sure the client side files do not reference any modules that are not available in the browser. These include imports of our functions with database access.
The Remix compiler in the past could reference the server side and client side functions from common helper files. Vite needs separate files for the server side and client side.
If a client side file imports a function that contains references to functionality that is not available in the browser, like file system or database access the application compiles without error, the server starts without error, but we will find error messages in the console window of the browser.
Module “events” has been externalized for browser compatibility. Cannot access “events.EventEmitter” in client code. See https://vite.dev/guide/troubleshooting.html#module-externalized-for-browser-compatibility for more details.
Uncaught ReferenceError: process is not defined at node_modules/pg/lib/defaults.js
In this example our client side helper file only imported, but not called a function that accessed the PostgreSQL database.
Another example, when a function (logInfo) is imported from the server side file, but not used. Solution: Delete the unused references
To import only a URL
RollupError]: “default” is not exported by ‘./index.css’ imported by “app/index.tsx”.
Style sheets are not compiled into the code, only the browser needs access to them to render the page. To reference style sheets, we only need to import the URL, so the compiler can make sure those are available and include them in the build. To import only the URL, add ?url to the end of the style sheet path.
import { LinksFunction } from "@remix-run/node";
-import styles from "./index.css";
+import styles from "./index.css?url";
Render UI only in the browser
Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: object. or React.jsx: type is invalid — expected a string (for built-in components) or a class/function (for composite components) but got: object.
Vite tries to render client side elements in the server. In the client side code render client side code only in the browser.
// Check if the code is running in a browser
const [isClient, setIsClient] = React.useState(false);
React.useEffect(() => {
setIsClient(true);
}, []);
# Render the UI
return (
<>
{isClient ? (
<Header/>
):null}
{isClient ? (
<div>
... The rest of the UI
</div>
):null}
{/* Display the Footer component */}
{isClient ? (
<Footer/>
):null}
</>
);
Custom image in the expandIcon
During the migration the compiler did not accept the Material UI icon library. You can use a custom PGN image for the expandIcon of the AccordionSummary:
Replace Material UI controls with standard HTML controls
When I ran my application in a Docker container I started to get error messages related to Material UI controls. I replaced those with standard HTML elements. See troubleshooting elow for the full error messages.
Material UI control
HTML element
Box
div
AppBar
div
Button
custom dropdown menu function
Material UI icon library
expandIcon={<img src=”/MY_IMAGE.png” />}
Troubleshooting
Internal server error: [vite] The requested module ‘…’ does not provide an export named ‘default’
[vite] Named export ‘json’ not found. The requested module ‘react-router’ is a CommonJS module, which may not support all module.exports as named exports.
Remove the json reference from the react-router import
import { json, redirect } from "react-router";
[vite] Named export 'GridColDef' not found. The requested module '@mui/x-data-grid' is a CommonJS module, which may not support all module.exports as named exports.
GridColDef is a type, import it with the type prefix. Quick actions can help
import {
DataGrid,
type GridColDef,
} from '@mui/x-data-grid';
(node:18) Warning: To load an ES module, set “type”: “module” in the package.json or use the .mjs extension. (Use node --trace-warnings ... to show where the warning was created) /app/node_modules/@mui/material/Box/index.js:1 export { default } from “./Box.js”; ^^^^^^
SyntaxError: Unexpected token ‘export’
When we run the application in a Docker container, we get the SyntaxError: Unexpected token ‘export’ error related to the Box.js. Remove references of <Box> from the application and replace those with <div>.
(node:18) Warning: To load an ES module, set “type”: “module” in the package.json or use the .mjs extension.
(Use `node –trace-warnings …` to show where the warning was created) /app/node_modules/@mui/material/AppBar/index.js:1
export { default } from “./AppBar.js”; ^^^^^^
SyntaxError: Unexpected token ‘export’
When we run the application in a Docker container, we get the SyntaxError: Unexpected token ‘export’ error related to the AppBar.js. Remove references of <AppBar> from the application and replace those with <div>.
(node:18) Warning: To load an ES module, set “type”: “module” in the package.json or use the .mjs extension.
(Use `node –trace-warnings …` to show where the warning was created) /app/node_modules/@mui/material/Button/index.js:1
export { default } from “./Button.js”; ^^^^^^
SyntaxError: Unexpected token ‘export’
When we run the application in a Docker container, we get the SyntaxError: Unexpected token ‘export’ error related to the Button.js. Remove references of <Button> from the application.
