Hi Mehram,

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

Database

For this example I have used of Northwind database that you can download using the link given below.

Download Northwind Database

HTML

<asp:GridView ID="gvDetails" runat="server" AutoGenerateColumns="false" OnRowDataBound="OnRowDataBound">
    <Columns>
        <asp:BoundField DataField="Narration" HeaderText="Narration">
            <HeaderStyle HorizontalAlign="Left" />
        </asp:BoundField>
    </Columns>
</asp:GridView>

Namespaces

C#

using System.Configuration;
using System.Data;
using System.Data.SqlClient;

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        string query = "SELECT TOP 5 Narration = ISNULL(t.ContactName, '') + CHAR(13) + CHAR(10) + ISNULL(t.Address, '') FROM Customers t";
        using (SqlConnection con = new SqlConnection(conString))
        {
            SqlCommand cmd = new SqlCommand(query);
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    gvDetails.DataSource = dt;
                    gvDetails.DataBind();
                }
            }
        }
    }
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        string[] stringSeparators = new string[] { "\r\n" };
        string[] texts = e.Row.Cells[0].Text.Split(stringSeparators, StringSplitOptions.None);
        if (texts.Length > 1)
        {
            e.Row.Cells[0].Text = string.Format("<b>{0}</b><br/>{1}", texts[0].Trim(), texts[1].Trim());
        }
        else
        {
            e.Row.Cells[0].Text = string.Format("<b>{0}</b>", texts[0].Trim());
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Dim query As String = "SELECT TOP 5 Narration = ISNULL(t.ContactName, '') + CHAR(13) + CHAR(10) + ISNULL(t.Address, '') FROM Customers t"
        Using con As SqlConnection = New SqlConnection(conString)
            Dim cmd As SqlCommand = New SqlCommand(query)
            Using sda As SqlDataAdapter = New SqlDataAdapter()
                cmd.Connection = con
                sda.SelectCommand = cmd
                Using dt As DataTable = New DataTable()
                    sda.Fill(dt)
                    gvDetails.DataSource = dt
                    gvDetails.DataBind()
                End Using
            End Using
        End Using
    End If
End Sub

Protected Sub OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim stringSeparators As String() = New String() {vbCrLf}
        Dim texts As String() = e.Row.Cells(0).Text.Split(stringSeparators, StringSplitOptions.None)
        If texts.Length > 1 Then
            e.Row.Cells(0).Text = String.Format("<b>{0}</b><br/>{1}", texts(0).Trim(), texts(1).Trim())
        Else
            e.Row.Cells(0).Text = String.Format("<b>{0}</b>", texts(0).Trim())
        End If
    End If
End Sub

Screenshot