Reading App.config XML file from .NET 8.0 Console and Web Applications

If you have worked with .NET before Core was released, you will be familiar with the App.config file. It is an XML settings file that was later replaced with JSON in .NET Core applications. If you still harbour a likeness to the XML App.config file, you will discover that it is still quite easy to use it for configuration settings instead of its JSON counterpart. In this article, we will read App.config settings from a .NET 8.0 console application and an ASP.NET 8.0 Razor Pages Application.

Companion Video: https://youtu.be/a_U4qNohkh0

Setup Console Application

In a suitable working folder, create a console application named ReadAppConfig with the following terminal window command:

dotnet new console -o ReadAppConfig

Change into the ReadingAppConfig folder with:

cd ReadAppConfig

Install the ConfigurationManager package with the following command:

dotnet add package System.Configuration.ConfigurationManager

The App.config file in Console Application

Create a file named App.config in the root of your application and add to it the following XML content:

<?xml version="1.0"?>

<configuration>

    <appSettings>

        <add key="endpoint" value="https://endpoint.somewhere.com/" />

    </appSettings>

    <connectionStrings>  

        <add

            name="sqlServer"

            providerName="System.Data.SqlClient"

            connectionString="Data Source=localhost;Initial Catalog=MyDB;Integrated Security=True;" />

    </connectionStrings>

</configuration>

The above file contains the following important settings:

1. an application setting named "endpoint" with value "https://endpoint.somewhere.com/"
2. a database connection string named "sqlServer" with value"Data Source=localhost;Initial Catalog=MyDB;Integrated Security=True;"

Program.cs in Console Application

Replace the contents of Program.cs with the following C# code:

using System.Configuration;

string _endpoint = ConfigurationManager.AppSettings["endpoint"]!;

string _connectionString = ConfigurationManager.ConnectionStrings["sqlServer"]!.ConnectionString;

Console.WriteLine($"Endpoint: {_endpoint}");

Console.WriteLine($"Connection String: {_connectionString}");  

Run Console Application

In a terminal window, run the app with the following command:

dotnet run

You should see the following output that verifies that information from App.config has successfully been read:

Endpoint: https://endpoint.somewhere.com/

Connection String: Data Source=localhost;Initial Catalog=MyDB;Integrated Security=True;

---

ASP.NET Razor Pages Application

Next, let us do the same thing in an ASP.NET Razor Pages Application.

Exit the previous console application and create a razor pages application is a separate folder with:

dotnet new razor -o ReadAppConfigWeb

Change to the folder containing the Razor Pages app with:

cd ReadAppConfigWeb 

Add the ConfigurationManager package with:

dotnet add package System.Configuration.ConfigurationManager

In the root folder of your ASP.NET Razor Pages application, add the same App.config file as before:

<?xml version="1.0"?>

<configuration>

    <appSettings>

        <add key="endpoint" value="https://endpoint.somewhere.com/" />

    </appSettings>

    <connectionStrings>  

        <add

            name="sqlServer"

            providerName="System.Data.SqlClient"

            connectionString="Data Source=localhost;Initial Catalog=MyDB;Integrated Security=True;" />

    </connectionStrings>

</configuration>

Open Pages/Index.cshtml.cs in your favourite editor and make the following changes to it:

1) Import System.Configuration with:

using Config = System.Configuration;

2) Add the following instance variables to the IndexModel class:

string _endpoint = Config.ConfigurationManager.AppSettings["endpoint"]!;

string _connectionString = Config.ConfigurationManager.ConnectionStrings["sqlServer"]!.ConnectionString;

3) Append these lines of code to the constructor:

_logger.LogInformation($"Endpoint: {_endpoint}");

_logger.LogInformation($"Connection String: {_connectionString}");

Now we can run the application with:

dotnet watch

In the terminal window you will notice the following output, which shows that the setting have indeed been read from App.config:

Endpoint: https://endpoint.somewhere.com.com/

Connection String: Data Source=localhost;Initial Catalog=MyDB;Integrated Security=True;

Conclusion

When using .NET Core, you can always resort to saving your configuration setting in an XML file instead of JSON. 

Export data in Excel format from an ASP.NET 6.0 Razor Pages Web App

Overview

In this tutorial I will show you how you can use the ClosedXML nuget package to export data in Excel format using an ASP.NET 6.0 Razor Pages web app. The data we will is is hard-coded student data. However, the approach works for data from any data source.

Source code: https://github.com/medhatelmasry/ExcelStar.git

Companion Video: https://youtu.be/8olaWPDKXyU

The environment I am using is: 

• https://github.com/medhatelmasry/OrdersChartRazorGoogleWrapper
• .NET version 6.0.100
• Visual Studio Code 

Project setup

Run the following command to create an ASP.NET Core Razor Pages application using .NET 6.0 in a folder named ExcelStar:

dotnet new razor -f net6.0 -o ExcelStar

Change directory into the new folder:

cd  ExcelStar

Install the ClosedXML nuget package with:

dotnet add package ClosedXML

Open the project inside VS Code with the following commands:

code .

Sample student data

Create a folder named Data. Inside the Data folder, create a Student.cs class file and add to it the following Student code:

public class Student {
    public int? Id { get; set; }
    public string? FirstName { get; set; }
    public string? LastName { get; set; }
    public string? School { get; set; }
    public static IEnumerable<Student> GetStudents() {
        int ndx = 0;
        List<Student> students = new List<Student>() {
            new Student() { Id = ++ndx, FirstName="Max", LastName="Pao", School="Science" },
            new Student() { Id = ++ndx, FirstName="Tom", LastName="Fay", School="Mining" },
            new Student() { Id = ++ndx, FirstName="Ann", LastName="Sun", School="Nursing" },                
            new Student() { Id = ++ndx, FirstName="Joe", LastName="Fox", School="Computing" },                
            new Student() { Id = ++ndx, FirstName="Sue", LastName="Mai", School="Mining" },                
            new Student() { Id = ++ndx, FirstName="Ben", LastName="Lau", School="Business" },                
            new Student() { Id = ++ndx, FirstName="Zoe", LastName="Ray", School="Mining" },                
            new Student() { Id = ++ndx, FirstName="Sam", LastName="Ash", School="Medicine" },                
            new Student() { Id = ++ndx, FirstName="Dan", LastName="Lee", School="Computing" },                
            new Student() { Id = ++ndx, FirstName="Pat", LastName="Day", School="Science" },                
            new Student() { Id = ++ndx, FirstName="Kim", LastName="Rex", School="Computing" },                
            new Student() { Id = ++ndx, FirstName="Tim", LastName="Ram", School="Business" },                
            new Student() { Id = ++ndx, FirstName="Rob", LastName="Wei", School="Mining" },                
            new Student() { Id = ++ndx, FirstName="Jan", LastName="Tex", School="Science" },                
            new Student() { Id = ++ndx, FirstName="Jim", LastName="Kid", School="Business" },                
            new Student() { Id = ++ndx, FirstName="Ben", LastName="Chu", School="Medicine" },                
            new Student() { Id = ++ndx, FirstName="Mia", LastName="Tao", School="Computing" },                
            new Student() { Id = ++ndx, FirstName="Ted", LastName="Day", School="Business" },                
            new Student() { Id = ++ndx, FirstName="Amy", LastName="Roy", School="Science" },                
            new Student() { Id = ++ndx, FirstName="Ian", LastName="Kit", School="Nursing" },                
            new Student() { Id = ++ndx, FirstName="Liz", LastName="Tan", School="Medicine" },                
            new Student() { Id = ++ndx, FirstName="Mat", LastName="Roy", School="Tourism" },                
            new Student() { Id = ++ndx, FirstName="Deb", LastName="Luo", School="Medicine" },                
            new Student() { Id = ++ndx, FirstName="Ana", LastName="Poe", School="Computing" },                
            new Student() { Id = ++ndx, FirstName="Lyn", LastName="Raj", School="Science" },                
            new Student() { Id = ++ndx, FirstName="Amy", LastName="Ash", School="Tourism" },                
            new Student() { Id = ++ndx, FirstName="Kim", LastName="Kid", School="Mining" },                
            new Student() { Id = ++ndx, FirstName="Bec", LastName="Fry", School="Nursing" },                
            new Student() { Id = ++ndx, FirstName="Eva", LastName="Lap", School="Computing" },                
            new Student() { Id = ++ndx, FirstName="Eli", LastName="Yim", School="Business" },                
            new Student() { Id = ++ndx, FirstName="Sam", LastName="Hui", School="Science" },                
            new Student() { Id = ++ndx, FirstName="Joe", LastName="Jin", School="Mining" },                
            new Student() { Id = ++ndx, FirstName="Liz", LastName="Kuo", School="Agriculture" },                
            new Student() { Id = ++ndx, FirstName="Ric", LastName="Mak", School="Tourism" },                
            new Student() { Id = ++ndx, FirstName="Pam", LastName="Day", School="Computing" },                
            new Student() { Id = ++ndx, FirstName="Stu", LastName="Gad", School="Business" },                
            new Student() { Id = ++ndx, FirstName="Tom", LastName="Bee", School="Tourism" },                
            new Student() { Id = ++ndx, FirstName="Bob", LastName="Lam", School="Agriculture" },                
            new Student() { Id = ++ndx, FirstName="Jim", LastName="Ots", School="Medicine" },                
            new Student() { Id = ++ndx, FirstName="Tom", LastName="Mag", School="Mining" },                
            new Student() { Id = ++ndx, FirstName="Hal", LastName="Doe", School="Agriculture" },                
            new Student() { Id = ++ndx, FirstName="Roy", LastName="Kim", School="Nursing" },                
            new Student() { Id = ++ndx, FirstName="Vis", LastName="Cox", School="Science" },                
            new Student() { Id = ++ndx, FirstName="Kay", LastName="Aga", School="Tourism" },                
            new Student() { Id = ++ndx, FirstName="Reo", LastName="Hui", School="Business" },               
            new Student() { Id = ++ndx, FirstName="Bob", LastName="Roe", School="Medicine" },                          
        };
        return students;
    }
}

The above provides us with suitable sample students data that we will later export into Excel format.

Export data to Excel format

Inside the Pages folder, add two files names Excel.cshtml & Excel.cshtml.cs. 

Content of Excel.cshtml, representing the view, will contain the following minimal code:

@page

@model ExcelModel

Excel.cshtml.cs is the code-behind file for the view and will contain the following minimal code:

using ClosedXML.Excel;

using ExcelStar.Data;

using Microsoft.AspNetCore.Mvc;

using Microsoft.AspNetCore.Mvc.RazorPages;

namespace ExcelStar.Pages;

public class ExcelModel : PageModel {

    private readonly ILogger<IndexModel> _logger;

    public ExcelModel(ILogger<IndexModel> logger) {

        _logger = logger;

    }

    public FileResult OnGet() {

        var data = Student.GetStudents();

        using (var workbook = new XLWorkbook()) {

            IXLWorksheet worksheet =

            workbook.Worksheets.Add("Students");

            worksheet.Cell(1, 1).Value = "Id";

            worksheet.Cell(1, 2).Value = "First";

            worksheet.Cell(1, 3).Value = "Last";

            worksheet.Cell(1, 4).Value = "School";

            IXLRange range = worksheet.Range(worksheet.Cell(1, 1).Address, worksheet.Cell(1, 4).Address);

            range.Style.Fill.SetBackgroundColor(XLColor.Almond);

            int index = 1;

            foreach (var item in data) {

                index++;

                worksheet.Cell(index, 1).Value = item.Id;

                worksheet.Cell(index, 2).Value = item.FirstName;

                worksheet.Cell(index, 3).Value = item.LastName;

                worksheet.Cell(index, 4).Value = item.School;

            }

            using (var stream = new MemoryStream()) {

                workbook.SaveAs(stream);

                var content = stream.ToArray();

                string contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

                var strDate = DateTime.Now.ToString("yyyyMMdd");

                string filename = string.Format($"Students_{strDate}.xlsx");

                return File(content, contentType, filename);

            }

        }

    }

}

What does the above code do?

1. Students are read into a variable named data.
2. A worksheet is created named Students with column titles Id, First, Last & School
3. The Students worksheet is added to the workbook.
4. The background color of the column titles is made to be the Almond color.
5. Thereafter, each row is filled with student data whereby Id goes into column 1, FirstName goes into column 2, LastName goes into column 3 and School goes into column 4.
6. The workbook is saved as a stream.
7. The stream is returned to the user as a file with a fixed name and an appropriate HTTP content type.

Adding Excel page to the navigation

We need to add our new page to the main navigation system. Edit Pages/Shared/_Layout.cshtml and add the following to the bottom of the <ul> . . . </ul> block:

<li class="nav-item">

<a class="nav-link text-dark" asp-area="" asp-page="/Excel">Export to Excel</a>

</li>

Testing our app

It is time to run our application with the following terminal window command:

dotnet watch

The application opens in your default browser and looks like this:

When you click on "Export to Excel", a file with extension .xlsx is downloaded to your default downloads folder. If you open this file in Excel, it should look like this:

Go ahead and explore other things you can do, like adding links, count, sum etc...

I hope you found this brief tutorial useful and that it satisfies your expectations.