Convert CSV file to Excel and Download from ASP.NET Angular Application

In this article you will see how to convert a CSV file to Excel file on server side ASP.NET application and download it from client side angular application

To convert the CSV file, you will use EPPlus package

Open Visual Studio
Create a new project using ASP.NET Core with Angular
Add Weather.csv inside wwwroot folder (refer code sample)
Install nuget package EPPlus
Open Controllers\WeatherForecastController.cs
Import using OfficeOpenXml;
Inject IWebHostEnvironment env in the constructor
Add the following code to convert csv file to excel and return the file in the response

[HttpGet("Download")]
public IActionResult Download()
{
    string csvFilePath = Path.Combine(env.WebRootPath, "Weather.csv");

    ExcelPackage.LicenseContext = LicenseContext.NonCommercial;
    var format = new ExcelTextFormat();
    format.Delimiter = ',';
    format.TextQualifier = '"';

    using var stream = new MemoryStream();
    using (var package = new ExcelPackage(stream))
    {
        ExcelWorksheet worksheet = package.Workbook.Worksheets.Add("Data");
        worksheet.Cells["A1"].LoadFromText(new FileInfo(csvFilePath), format, OfficeOpenXml.Table.TableStyles.Medium27, FirstRowIsHeader: true);
        package.Save();
    }
    return File(stream.ToArray(), "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
}

In ClientApp\src\app\fetch-data\fetch-data.component.html add a button to download the excel file

<button type="button" (click)="downloadExcelFromCSV()">Download Excel From CSV</button>

In ClientApp\src\app\fetch-data\fetch-data.component.ts add the method to download the file from the ASP.Net API.
Set the responseType to blob in the httpHeader of angular http call.
Also set the MIME-Type when creating Blob from the response. application/octet-stream or application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

downloadExcelFromCSV() {
    this.http.get(this.baseUrl + 'weatherforecast/download', { responseType: 'blob' }).subscribe(data => {
      // Filename autogenerated
      //const blob = new Blob([data], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' });
      //const url = window.URL.createObjectURL(blob);
      //window.open(url);

      // For Fixed Filename
      var link = document.createElement('a');
      link.href = window.URL.createObjectURL(data);
      link.download = "data.xlsx";
      link.click();
    })
  }

Convert CSV file to Excel and Download from ASP.NET Angular Application

Try Sample

Access Code

References