This article shows some alternatives to write text to a file with C# in ASP.NET Core. You may want to write text to a file to export data, to debug your program or to output information from your program.
Create a CSV file
A CSV file is a text file where the data is separated by comma (,) on each row, you can use other characters to separate data. A CSV file can be imported in Excel or in Open Office Calc for example.
using (StreamWriter writer = new StreamWriter("D:\\MyFolder\\TEST\\Files\\case.txt"))
{
for (int i = 0; i < input.Length; i++)
{
writer.WriteLine(input[i].text + "," + input[i].powerofbase
+ "," + input[i].int_value.ToString(CultureInfo.InvariantCulture)
+ "," + input[i].decimal_value.ToString(CultureInfo.InvariantCulture)
+ "," + input[i].last_numbers.ToString(CultureInfo.InvariantCulture)
+ "," + input[i].index);
}
}Create an XML file
The code below shows an example of the creation of a sitemap in XML-format. The environment variable is used to get the web root path of the application.
public class SitemapRepository : ISitemapRepository
{
#region Variables
private readonly IWebHostEnvironment environment;
private readonly IStaticPageRepository static_page_repository;
private readonly IGroupRepository group_repository;
#endregion
#region Constructors
public SitemapRepository(IWebHostEnvironment environment, IStaticPageRepository static_page_repository, IGroupRepository group_repository)
{
// Set values for instance variables
this.environment = environment;
this.static_page_repository = static_page_repository;
this.group_repository = group_repository;
} // End of the constructor
#endregion
#region Methods
public void CreateSitemap()
{
// Create the directory path
string directoryPath = this.environment.WebRootPath + "\\sitemaps\\";
// Check if the directory exists
if (System.IO.Directory.Exists(directoryPath) == false)
{
// Create the directory
System.IO.Directory.CreateDirectory(directoryPath);
}
// Create the file
string filepath = directoryPath + "Sitemap.xml.gz";
// Get static pages and groups
IList<StaticPage> staticPages = this.static_page_repository.GetAllActiveLinks("title", "ASC");
IList<Group> groups = this.group_repository.GetAll("title", "ASC");
// Create variables
GZipStream gzipStream = null;
XmlWriter xmlTextWriter = null;
try
{
// Create a gzip stream
gzipStream = new GZipStream(new FileStream(filepath, FileMode.Create), CompressionMode.Compress);
// Create a xml text writer
XmlWriterSettings xwSettings = new XmlWriterSettings
{
Encoding = new UTF8Encoding(true)
};
xmlTextWriter = XmlWriter.Create(gzipStream, xwSettings);
// Write the start of the document
xmlTextWriter.WriteStartDocument();
// Write the url set for the xml document <urlset>
xmlTextWriter.WriteStartElement("urlset", "http://www.sitemaps.org/schemas/sitemap/0.9");
xmlTextWriter.WriteAttributeString("xmlns", "image", null, "http://www.google.com/schemas/sitemap-image/1.1");
xmlTextWriter.WriteAttributeString("xmlns", "video", null, "http://www.google.com/schemas/sitemap-video/1.1");
// Create the start string
string baseUrl = "https://www.mysite.se";
// Add the baseurl
CreateUrlPost(xmlTextWriter, baseUrl, "1.0", "monthly", DateTime.UtcNow);
// Loop static pages
for (int i = 0; i < staticPages.Count; i++)
{
// Create the url post
if (staticPages[i].meta_robots.StartsWith("index") == true)
{
CreateUrlPost(xmlTextWriter, baseUrl + "/home/page/" + staticPages[i].page_name, "0.9", "monthly", DateTime.UtcNow);
}
}
// Loop groups
for (int i = 0; i < groups.Count; i++)
{
// Create the url post
if(groups[i].meta_robots.StartsWith("index") == true)
{
CreateUrlPost(xmlTextWriter, baseUrl + "/home/group/" + groups[i].page_name, "0.2", "monthly", DateTime.UtcNow);
}
}
// Write the end tag for the xml document </urlset>
xmlTextWriter.WriteEndDocument();
// Flush the writer
xmlTextWriter.Flush();
}
catch (Exception e)
{
throw e;
}
finally
{
// Close streams
if (xmlTextWriter != null)
{
// Close the XmlTextWriter
xmlTextWriter.Dispose();
}
if (gzipStream != null)
{
// Close the gzip stream
gzipStream.Dispose();
}
}
} // End of the CreateSitemap method
private void CreateUrlPost(XmlWriter xmlTextWriter, string url, string priority, string changeFrequency, DateTime lastModifiedDate)
{
xmlTextWriter.WriteStartElement("url");
xmlTextWriter.WriteStartElement("loc");
xmlTextWriter.WriteString(url);
xmlTextWriter.WriteEndElement();
xmlTextWriter.WriteStartElement("lastmod");
xmlTextWriter.WriteString(string.Format("{0:yyyy-MM-dd}", lastModifiedDate));
xmlTextWriter.WriteEndElement();
xmlTextWriter.WriteStartElement("changefreq");
xmlTextWriter.WriteString(changeFrequency);
xmlTextWriter.WriteEndElement();
xmlTextWriter.WriteStartElement("priority");
xmlTextWriter.WriteString(priority);
xmlTextWriter.WriteEndElement();
xmlTextWriter.WriteEndElement();
} // End of the CreateUrlPost method
#endregion
} // End of the classWrite to log-file
The example below shows how you can append a line of text to a log file. The file is created automatically if does not exist. The directory must exist.
private void LogError(string error)
{
// Set the file path
string path = this.directory + "\\errors.txt";
// Add the error message to the file
System.IO.File.AppendAllText(path, $"{DateTime.Now.ToString("o")} [ERR] {error}" + Environment.NewLine);
} // End of the LogError methodCreate a JSON file
You can serialize a model to a JSON file. The example below shows how to get applications settings from a JSON file and how to save modified settings to a JSON file.
string path = this.directory + "\\appsettings.json";
// Get the data
string data = System.IO.File.ReadAllText(path, Encoding.UTF8);
// Convert data to app settings
AppSettings app_settings = JsonConvert.DeserializeObject<AppSettings>(data);
// Modify application settings
// Write updated application settings to the file
System.IO.File.WriteAllText(path, JsonConvert.SerializeObject(app_settings, Formatting.Indented));public class AppSettings
{
#region Variables
public Logging Logging { get; set; }
public DoxservrOptions DoxservrOptions { get; set; }
public FortnoxOptions FortnoxOptions { get; set; }
public DefaultValues DefaultValues { get; set; }
#endregion
#region Constructors
public AppSettings()
{
// Set values for instance variables
this.Logging = new Logging();
this.DoxservrOptions = new DoxservrOptions();
this.FortnoxOptions = new FortnoxOptions();
this.DefaultValues = new DefaultValues();
} // End of the constructor
#endregion
} // End of the class