Generate Report via Converting Data table to HTML in .net core API.

C#

Generate Report via Converting Data table to HTML in .net core API.

In this tutorial we will learn how to generate files for reporting purposes without using any third party library.

During projects i found lot of situations when client want to see end reports for data and he want to finish this work within a day. This tutorial helps you to generate reports in very less time.

We will be generating reports in HTML format and we will be printing datatable to HTML file.

Let's start

a. Create .Net core API.

b. Create Endpoint for Download file

c. Make a call to database and fetch data.

d. Create report in html format and send html file back to user as response.

Consider we connect to database and get below data table

Consider code below

csharp
using Microsoft.AspNetCore.Mvc;
using System.Data;
using System.Text;

// For more information on enabling Web API for empty projects, visit https://go.microsoft.com/fwlink/?LinkID=397860

namespace DownloadFile.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class DownloadFile : ControllerBase
    {
        // GET: api/<DownloadFile>
        [HttpGet]
        public ActionResult GetFileDownload()
        {
            DataTable dt = GetDataFromDatabase();
            string HtmlBody = ExportDatatableToHtml(dt);

            var contentType = "text/xml";
            var bytes = Encoding.UTF8.GetBytes(HtmlBody);
            var result = new FileContentResult(bytes, contentType);
            result.FileDownloadName = "Report.html";
            return result;
          
        }

        protected string ExportDatatableToHtml(DataTable dt)
        {
          ///   using html code we are creating html file and printing datatable.
            StringBuilder strHTMLBuilder = new StringBuilder();
            strHTMLBuilder.Append("<html >");
            strHTMLBuilder.Append("<head>");
            strHTMLBuilder.Append("</head>");
            strHTMLBuilder.Append("<body>");
            strHTMLBuilder.Append("<table border='1px' cellpadding='1' cellspacing='1' bgcolor='lightyellow' style='font-family:Garamond; font-size:smaller'>");
            strHTMLBuilder.Append("<tr >");
            foreach (DataColumn myColumn in dt.Columns)
            {
                strHTMLBuilder.Append("<td >");
                strHTMLBuilder.Append(myColumn.ColumnName);
                strHTMLBuilder.Append("</td>");
            }
            strHTMLBuilder.Append("</tr>");

            foreach (DataRow myRow in dt.Rows)
            {
                strHTMLBuilder.Append("<tr >");
                foreach (DataColumn myColumn in dt.Columns)
                {
                    strHTMLBuilder.Append("<td >");
                    strHTMLBuilder.Append(myRow[myColumn.ColumnName].ToString());
                    strHTMLBuilder.Append("</td>");
                }
                strHTMLBuilder.Append("</tr>");
            }
            //Close tags.
            strHTMLBuilder.Append("</table>");
            strHTMLBuilder.Append("</body>");
            strHTMLBuilder.Append("</html>");
            string Htmltext = strHTMLBuilder.ToString();
            return Htmltext;
        }

        private DataTable GetDataFromDatabase()
        {
            // make call to database int this case we hadcoded datatable.

            DataTable table = new DataTable();
            table.Columns.Add("ID", typeof(int));
            table.Columns.Add("NAME", typeof(string));
            table.Columns.Add("CITY", typeof(string));

            table.Rows.Add(111, "Devesh", "Ghaziabad");
            table.Rows.Add(222, "Nikhil", "United State");
            table.Rows.Add(102, "himanshu", "Canada");
            table.Rows.Add(456, "Kapil", "Dubai");
            table.Rows.Add(3345, "Sanjay", "Germany");

            return table;
        }

    }
}

Understanding code.

a. We have created GetFileDownload() Endpoint

b. We are making call to database function name -> GetDataFromDatabase , in real time use case please replace hard coded datatable with actual data from database.

c. We have created Function to convert Datatable to HTML file

d. We are iterating each row of datatable and formatting rows and columns using very simple tr and td tags.

strHTMLBuilder.Append("<tr >");

csharp
            foreach (DataColumn myColumn in dt.Columns)
            {
                strHTMLBuilder.Append("<td >");
                strHTMLBuilder.Append(myColumn.ColumnName);
                strHTMLBuilder.Append("</td>");
            }
            strHTMLBuilder.Append("</tr>");

            foreach (DataRow myRow in dt.Rows)
            {
                strHTMLBuilder.Append("<tr >");
                foreach (DataColumn myColumn in dt.Columns)
                {
                    strHTMLBuilder.Append("<td >");
                    strHTMLBuilder.Append(myRow[myColumn.ColumnName].ToString());
                    strHTMLBuilder.Append("</td>");
                }
                strHTMLBuilder.Append("</tr>");
            }

e. Download code has FileContentResult Which inherits from ActionResult. we are converting html string into bytes and encapsulating bytes into FileContentResult class and returning as result

csharp
[HttpGet]
        public ActionResult GetFileDownload()
        {
            DataTable dt = GetDataFromDatabase();
            string HtmlBody = ExportDatatableToHtml(dt);

            var contentType = "text/xml";
            var bytes = Encoding.UTF8.GetBytes(HtmlBody);
            var result = new FileContentResult(bytes, contentType);
            result.FileDownloadName = "Report.html";
            return result;
           
        }

Running application

Click on execute button

Download file.

Open File. We have opened file in browser.

We are ready with report.

Conclusion

This is quick way to generate file in html format. Above code is 100 % working and fast because we are not using and third-party library to create files.

C#

Generate Report via Converting Data table to HTML in .net core API.

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