Hi indradeo,

Refer below code.

HTML

<asp:GridView ID="GridView1" runat="server" ShowHeader="false" Font-Bold="true" Font-Size="37px"
    RowStyle-Font-Names="Calibri" RowStyle-ForeColor="White" RowStyle-BackColor="#2514"
    RowStyle-BorderStyle="None" RowStyle-BorderColor="Red" CellPadding="0"
    OnRowDataBound="Gridview1_OnRowDataBound" CssClass="auto-style1" Width="923px">
</asp:GridView>

Namespaces

C#

using System.Data;
using System.Drawing;
using System.Net;

VB.Net

Imports System.Data
Imports System.Drawing
Imports System.Net

Code

C#

static string[] lines;
int i = 0;
protected void Page_Load(object sender, EventArgs e)
{
    string textFromFile = (new WebClient()).DownloadString("http://10.1.246.41/AAQMS/CEMS/ReadTxtFile/Test.txt");
    lines = textFromFile.Split('\n');
    DataTable dt = new DataTable();
    dt.Columns.Add(new DataColumn("Data", System.Type.GetType("System.String")));
    for (int i = 0; i < lines.Length; i++)
    {
        DataRow dr = dt.NewRow();
        dr["Data"] = "" + " " + " " + " " + lines[i] + " " + "MB";
        dt.Rows.Add(dr);
        dr = dt.NewRow();
    }
    GridView1.DataSource = dt;
    GridView1.DataBind();
}
protected void Gridview1_OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        e.Row.Cells[0].ForeColor = System.Drawing.Color.White;
        string line = e.Row.RowIndex % 2 != 0 ? lines[i] : "";
        if (e.Row.RowIndex % 2 != 0)
        {
            if (line.Length <= 200)
            {
                e.Row.Cells[0].BackColor = System.Drawing.Color.Red;
            }
            else if (line.Length >= 100 && line.Length <= 0)
            {
                e.Row.Cells[0].BackColor = System.Drawing.Color.Orange;
            }
            else
            {
                e.Row.Cells[0].BackColor = System.Drawing.Color.Green;
            }
        }
        i++;
    }
}
protected void OnDataBound(object sender, EventArgs e)
{
    GridViewRow row = new GridViewRow(0, 0, DataControlRowType.Header, DataControlRowState.Normal);
    TableHeaderCell cell = new TableHeaderCell();
    cell.Text = "CEMS Realtime Data UNIT#2";
    cell.ColumnSpan = 2;
    row.Controls.Add(cell);
    row.BackColor = ColorTranslator.FromHtml("#3AC0F2");
    GridView1.HeaderRow.Parent.Controls.AddAt(0, row);
}

VB.Net

Shared lines As String()
Private i As Integer = 0

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Dim textFromFile As String = (New WebClient()).DownloadString("http://10.1.246.41/AAQMS/CEMS/ReadTxtFile/Test.txt")
    lines = textFromFile.Split(vbLf)
    Dim dt As DataTable = New DataTable()
    dt.Columns.Add(New DataColumn("Data", System.Type.[GetType]("System.String")))

    For i As Integer = 0 To lines.Length - 1
        Dim dr As DataRow = dt.NewRow()
        dr("Data") = "" & " " & " " & " " & lines(i) & " " & "MB"
        dt.Rows.Add(dr)
        dr = dt.NewRow()
    Next

    GridView1.DataSource = dt
    GridView1.DataBind()
End Sub

Protected Sub Gridview1_OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        e.Row.Cells(0).ForeColor = System.Drawing.Color.White
        Dim line As String = If(e.Row.RowIndex Mod 2 <> 0, lines(i), "")
        If e.Row.RowIndex Mod 2 <> 0 Then
            If line.Length <= 200 Then
                e.Row.Cells(0).BackColor = System.Drawing.Color.Red
            ElseIf line.Length >= 100 AndAlso line.Length <= 0 Then
                e.Row.Cells(0).BackColor = System.Drawing.Color.Orange
            Else
                e.Row.Cells(0).BackColor = System.Drawing.Color.Green
            End If
        End If

        i += 1
    End If
End Sub

Protected Sub OnDataBound(ByVal sender As Object, ByVal e As EventArgs)
    Dim row As GridViewRow = New GridViewRow(0, 0, DataControlRowType.Header, DataControlRowState.Normal)
    Dim cell As TableHeaderCell = New TableHeaderCell()
    cell.Text = "CEMS Realtime Data UNIT#2"
    cell.ColumnSpan = 2
    row.Controls.Add(cell)
    row.BackColor = ColorTranslator.FromHtml("#3AC0F2")
    GridView1.HeaderRow.Parent.Controls.AddAt(0, row)
End Sub