Read csv file and display result in GridView group by RefId and save in database using C# in ASP.Net

Hi born2achie,

I have created a sample which full fill your requirement

HTML

<div>
    <asp:FileUpload ID="FileUpload1" runat="server" />
    <asp:Button Text="Upload" OnClick="OnCLick" runat="server" />
    <asp:GridView ID="gvCSVDetails" runat="server" />
</div>

C#

protected void OnCLick(object sender, EventArgs e)
{
    //Upload and save the file
    string csvPath = Server.MapPath("~/Files/") + Path.GetFileName(FileUpload1.PostedFile.FileName);
    FileUpload1.SaveAs(csvPath);

    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[3] { new DataColumn("Id", typeof(int)), new DataColumn("RefID", typeof(string)), new DataColumn("Data", typeof(string)) });

    string csvData = File.ReadAllText(csvPath);
    foreach (string row in csvData.Split('\n'))
    {
        if (!string.IsNullOrEmpty(row))
        {
            dt.Rows.Add();
            int i = 0;
            foreach (string cell in row.Split(','))
            {
                dt.Rows[dt.Rows.Count - 1][i] = cell;
                i++;
            }
        }
    }
    DataTable sortedData = dt.Clone();
    string data = string.Empty;
    string refId = string.Empty;
    for (int i = 0; i < dt.Rows.Count; i++)
    {
        DataRow dr = sortedData.NewRow();
        refId = dt.Rows[i]["RefID"].ToString();
        for (int j = 0; j < dt.Rows.Count; j++)
        {
            if (refId == dt.Rows[j]["RefID"].ToString())
            {
                data = data + dt.Rows[j]["Data"].ToString() + "|";
            }
        }
        if (i > 0)
        {
            if (dt.Rows[i]["RefID"].ToString() != dt.Rows[i - 1]["RefID"].ToString())
            {
                dr["Id"] = dt.Rows[i]["Id"].ToString();
                dr["RefID"] = dt.Rows[i]["RefID"].ToString();
                dr["Data"] = data.Remove(data.Length - 1);
            }
        }
        else
        {
            dr["Id"] = dt.Rows[i]["Id"].ToString();
            dr["RefID"] = dt.Rows[i]["RefID"].ToString();
            dr["Data"] = data.Remove(data.Length - 1);
        }
        sortedData.Rows.Add(dr);
        data = string.Empty;

    }
    for (int i = sortedData.Rows.Count - 1; i >= 0; i += -1)
    {
        DataRow row = sortedData.Rows[i];
        if (row.ItemArray[0] == null)
        {
            sortedData.Rows.Remove(row);
        }
        else if (string.IsNullOrEmpty(row.ItemArray[0].ToString()))
        {
            sortedData.Rows.Remove(row);
        }
    }
    sortedData = sortedData.DefaultView.ToTable(true);
    string consString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(consString))
    {
        using (SqlBulkCopy sqlBulkCopy = new SqlBulkCopy(con))
        {
            //Set the database table name
            sqlBulkCopy.DestinationTableName = "dbo.Customers";
            con.Open();
            sqlBulkCopy.WriteToServer(sortedData);
            con.Close();
        }
    }
    gvCSVDetails.DataSource = sortedData;
    gvCSVDetails.DataBind();
}

ScreenShot

thank you