Läs text från fil i ASP.NET Core

Denna artikel visar några alternativ för att läsa in text från en fil med C# i ASP.NET Core. Du kanske vill läsa text från en fil för att importera data eller för att få inmatning till ditt program.

Inläsning från CSV-fil

En CSV-fil är en textfil där data på varje rad skiljs åt av kommatecken (,), andra tecken kan användas som separatorer. En CSV-fil kan exporteras från Excel eller Open Office Calc till exempel.

List<string[]> values = new List<string[]>();
using (StreamReader reader = new StreamReader("D:\\MyFolder\\Files\\case.txt"))
{
    while(!reader.EndOfStream)
    {
        values.Add(reader.ReadLine().Split(','));
    }
}

Inläsning från XML-fil

XML-filer används ofta i olika standarder och liknar HTML. Koden nedan visar ett exempel på inläsning av lag från en XML-fil som representerar en tabell.

<standings>
	<team>
		<name>Malmö FF</name>
		<games>7</games>
		<wins>4</wins>
		<ties>2</ties>
		<losses>1</losses>
		<goals>12-7 (5)</goals>
		<points>14</points>
	</team>
	<team>
		<name>IFK Göteborg</name>
		<games>7</games>
		<wins>4</wins>
		<ties>1</ties>
		<losses>2</losses>
		<goals>16-9 (7)</goals>
		<points>13</points>
	</team>
	<team>
		<name>BK Häcken</name>
		<games>7</games>
		<wins>4</wins>
		<ties>1</ties>
		<losses>2</losses>
		<goals>10-4 (6)</goals>
		<points>13</points>
	</team>
</standings>

public class TeamInGroupStanding
{
    #region Variables

    public string name { get; set; }
    public string games { get; set; }
    public string wins { get; set; }
    public string ties { get; set; }
    public string losses { get; set; }
    public string goals { get; set; }
    public string points { get; set; }

    #endregion

    #region Constructors

    public TeamInGroupStanding()
    {
        // Set values for instance variables
        this.name = "";
        this.games = "";
        this.wins = "";
        this.ties = "";
        this.losses = "";
        this.goals = "";
        this.points = "";

    } // End of the constructor

    #endregion

} // End of the class

public IList<TeamInGroupStanding> GetTeamsFromXml(string xmlString)
{
    // Create the list to return
    IList<TeamInGroupStanding> posts = new List<TeamInGroupStanding>(12);

    try
    {
        // Create the xml document
        XDocument xmlDocument = XDocument.Parse(xmlString);

        // Get all the team nodes
        IEnumerable<XElement> nodeList = xmlDocument.Descendants("team");

        foreach (XElement node in nodeList)
        {
            // Create a new team in group standings
            TeamInGroupStanding team = new TeamInGroupStanding();

            // Get all the data from the xml document
            team.name = node.Element("name").Value;
            team.games = node.Element("games").Value;
            team.wins = node.Element("wins").Value;
            team.ties = node.Element("ties").Value;
            team.losses = node.Element("losses").Value;
            team.goals = node.Element("goals").Value;
            team.points = node.Element("points").Value;

            // Add the team to the list
            posts.Add(team);
        }
    }
    catch (Exception ex)
    {
        string exMessage = ex.Message;
    }

    // Return the list of posts
    return posts;

} // End of the GetTeamsFromXml method

Läs all text som en sträng

Koden nedan visar ett exempel på inläsning av all text från en fil till en sträng.

string path = "D:\\MyFolder\\Files\\myfile.json";

// Get the data
string data = System.IO.File.ReadAllText(path, Encoding.UTF8);

Inläsning från JSON-fil

Du kan deserialisera en JSON-fil till en modell i C#. Koden nedan visar hur man kan läsa in all text från en JSON-fil och deserialisera strängen till en modell.

// Document
AnnytabDoxTrade doc = null;
string file_path = "D:\\MyFolder\\Files\\myfile.json";

try
{
    // Get file data
    string file_data = System.IO.File.ReadAllText(file_path, Encoding.UTF8);

    // Make sure that there is file data
    if(string.IsNullOrEmpty(file_data) == true)
    {
        // Log the error
        this.logger.LogError($"File is empty: {file_path}.");
    }

    // Get the document
    doc = JsonConvert.DeserializeObject<AnnytabDoxTrade>(file_data);
}
catch(Exception ex)
{
    // Log the error
    this.logger.LogError(ex, $"Deserialize file: {file_path}", null);
}

public class AnnytabDoxTrade
{
    #region Variables

    public string id { get; set; }
    public string document_type { get; set; }
    public string payment_reference { get; set; }
    public string issue_date { get; set; }
    public string due_date { get; set; }
    public string delivery_date { get; set; }
    public string offer_expires_date { get; set; }
    public IDictionary<string, string> seller_references { get; set; }
    public IDictionary<string, string> buyer_references { get; set; }
    public string terms_of_delivery { get; set; }
    public string terms_of_payment { get; set; }
    public string mode_of_delivery { get; set; }
    public decimal? total_weight_kg { get; set; }
    public decimal? penalty_interest { get; set; }
    public string currency_code { get; set; }
    public string vat_country_code { get; set; }
    public string vat_state_code { get; set; }
    public string comment { get; set; }
    public PartyInformation seller_information { get; set; }
    public PartyInformation buyer_information { get; set; }
    public PartyInformation delivery_information { get; set; }
    public IList<PaymentOption> payment_options { get; set; }
    public IList<ProductRow> product_rows { get; set; }
    public IList<VatSpecification> vat_specification { get; set; }
    public decimal? subtotal { get; set; }
    public decimal? vat_total { get; set; }
    public decimal? rounding { get; set; }
    public decimal? total { get; set; }
    public decimal? paid_amount { get; set; }
    public decimal? balance_due { get; set; }

    #endregion

    #region Constructors

    public AnnytabDoxTrade()
    {
        // Set values for instance variables
        this.id = null;
        this.document_type = null;
        this.payment_reference = null;
        this.issue_date = null;
        this.due_date = null;
        this.delivery_date = null;
        this.offer_expires_date = null;
        this.seller_references = null;
        this.buyer_references = null;
        this.terms_of_delivery = null;
        this.terms_of_payment = null;
        this.mode_of_delivery = null;
        this.total_weight_kg = null;
        this.penalty_interest = null;
        this.currency_code = null;
        this.vat_country_code = null;
        this.vat_state_code = null;
        this.comment = null;
        this.seller_information = null;
        this.buyer_information = null;
        this.delivery_information = null;
        this.payment_options = null;
        this.product_rows = null;
        this.vat_specification = null;
        this.subtotal = null;
        this.vat_total = null;
        this.rounding = null;
        this.total = null;
        this.paid_amount = null;
        this.balance_due = null;

    } // End of the constructor

    #endregion

    #region Get methods

    public override string ToString()
    {
        return JsonConvert.SerializeObject(this);

    } // End of the ToString method

    #endregion

} // End of the class