Export HTML contents from database table to Excel file using C# and VB.Net in ASP.Net

Hi comunidadmexi...,

Check this example. Now please take its reference and correct your code.

Namespaces

C#

using System.Data;
using System.Drawing;
using System.IO;
using System.Text;
using System.Threading;

VB.Net

Imports System.Data
Imports System.Drawing
Imports System.IO
Imports System.Text
Imports System.Threading

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    MTxlssp();
}

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        for (int i = 0; i < e.Row.Cells.Count; i++)
        {
            string encoded = e.Row.Cells[i].Text.Trim();
            e.Row.Cells[i].Text = Context.Server.HtmlDecode(encoded);
        }
    }
}

public override void VerifyRenderingInServerForm(Control control)
{

}

private DataTable GetData()
{
    DataTable dt = new DataTable();
    dt.Columns.Add("Contents");
    dt.Rows.Add("<p><h3><span style=color:#0000ff;><strong>test</strong></span></h3></p>");
    dt.Rows.Add("<h4><strong>- test1</strong></h4>");
    dt.Rows.Add("<h4><strong>- test2</strong></h4>");
    return dt;
}

private void MTxlssp()
{
    DataTable dt = GetData();
    GridView GridView1 = new GridView
    {
        AllowPaging = false,
        DataSource = dt
    };
    GridView1.RowDataBound += GridView1_RowDataBound;

    GridView1.DataBind();

    Thread.Sleep(3000);
    Response.Clear();
    Response.Buffer = true;
    Response.Charset = "";
    Response.ContentEncoding = Encoding.UTF8;
    Response.ContentType = "application/vnd.ms-excel";
    Response.AddHeader("content-disposition", "attachment;filename=test.xls");
    HttpCookie cookie2 = new HttpCookie("ExcelDownloadFlag")
    {
        Value = "Flag",
        Expires = DateTime.Now.AddDays(1)
    };
    Response.AppendCookie(cookie2);

    using (StringWriter sw = new StringWriter())
    {
        HtmlTextWriter hw = new HtmlTextWriter(sw);

        GridView1.HeaderRow.BackColor = Color.White;

        foreach (TableCell cell in GridView1.HeaderRow.Cells)
        {
            cell.BackColor = GridView1.HeaderStyle.BackColor;
        }
        foreach (GridViewRow row in GridView1.Rows)
        {
            row.BackColor = Color.White;
            foreach (TableCell cell in row.Cells)
            {
                if (row.RowIndex % 2 == 0)
                {
                    cell.BackColor = GridView1.AlternatingRowStyle.BackColor;
                }
                else
                {
                    cell.BackColor = GridView1.RowStyle.BackColor;
                }
                cell.CssClass = "textmode";
            }
        }

        GridView1.RenderControl(hw);
        string style = @"<style> .textmode { } </style>";
        Response.Write(style);
        Response.Output.Write(sw.ToString());
        Response.Flush();
        Response.End();
    }
}

VB.Net

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    MTxlssp()
End Sub
Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then

        For i As Integer = 0 To e.Row.Cells.Count - 1
            Dim encoded As String = e.Row.Cells(i).Text.Trim()
            e.Row.Cells(i).Text = Context.Server.HtmlDecode(encoded)
        Next
    End If
End Sub

Public Overrides Sub VerifyRenderingInServerForm(ByVal control As Control)
End Sub

Private Function GetData() As DataTable
    Dim dt As DataTable = New DataTable()
    dt.Columns.Add("Contents")
    dt.Rows.Add("<p><h3><span style=color:#0000ff;><strong>test</strong></span></h3></p>")
    dt.Rows.Add("<h4><strong>- test1</strong></h4>")
    dt.Rows.Add("<h4><strong>- test2</strong></h4>")
    Return dt
End Function

Private Sub MTxlssp()
    Dim dt As DataTable = GetData()
    Dim GridView1 As GridView = New GridView With {
        .AllowPaging = False,
        .DataSource = dt
    }
    AddHandler GridView1.RowDataBound, AddressOf GridView1_RowDataBound
    GridView1.DataBind()

    Thread.Sleep(3000)
    Response.Clear()
    Response.Buffer = True
    Response.Charset = ""
    Response.ContentEncoding = Encoding.UTF8
    Response.ContentType = "application/vnd.ms-excel"
    Response.AddHeader("content-disposition", "attachment;filename=test.xls")
    Dim cookie2 As HttpCookie = New HttpCookie("ExcelDownloadFlag") With {
        .Value = "Flag",
        .Expires = DateTime.Now.AddDays(1)
    }
    Response.AppendCookie(cookie2)

    Using sw As StringWriter = New StringWriter()
        Dim hw As HtmlTextWriter = New HtmlTextWriter(sw)
        GridView1.HeaderRow.BackColor = Color.White
        For Each cell As TableCell In GridView1.HeaderRow.Cells
            cell.BackColor = GridView1.HeaderStyle.BackColor
        Next
        For Each row As GridViewRow In GridView1.Rows
            row.BackColor = Color.White
            For Each cell As TableCell In row.Cells
                If row.RowIndex Mod 2 = 0 Then
                    cell.BackColor = GridView1.AlternatingRowStyle.BackColor
                Else
                    cell.BackColor = GridView1.RowStyle.BackColor
                End If
                cell.CssClass = "textmode"
            Next
        Next

        GridView1.RenderControl(hw)
        Dim style As String = "<style> .textmode { } </style>"
        Response.Write(style)
        Response.Output.Write(sw.ToString())
        Response.Flush()
        Response.End()
    End Using
End Sub

Screenshot