Display all records if value is Empty or NULL using Linq in ASP.Net

Hi ramco1917,

Please refer below sample.

Database

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

Download Northwind Database

HTML

<asp:TextBox ID="txtSearch" runat="server"></asp:TextBox><br />
<asp:Button ID="btnFilter" runat="server" Text="Search" OnClick="OnSearch" />
<asp:GridView ID="gvOrders" runat="server" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="OrderID" HeaderText="OrderID" />
        <asp:BoundField DataField="ShipName" HeaderText="ShipName" />
        <asp:BoundField DataField="ShipCountry" HeaderText="ShipCountry" />
    </Columns>
</asp:GridView>

Namespace

C#

using NORTHWINDModel;

VB.Net

Imports NORTHWINDModel

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        NORTHWINDEntities entities = new NORTHWINDEntities();
        List<Order> orders = entities.Orders.Take(10).ToList();
        BindGrid(orders);
    }
}

protected void OnSearch(object sender, EventArgs e)
{
    NORTHWINDEntities entities = new NORTHWINDEntities();
    List<Order> orders = entities.Orders.Take(10).ToList();
    if (!string.IsNullOrEmpty(txtSearch.Text.Trim()))
    {
        orders = orders.Where(x => x.ShipCountry == txtSearch.Text.Trim()).ToList();
    }
    BindGrid(orders);
}

private void BindGrid(List<Order> orders)
{
    gvOrders.DataSource = orders;
    gvOrders.DataBind();
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim entities As NORTHWINDEntities = New NORTHWINDEntities()
        Dim orders As List(Of Order) = entities.Orders.Take(10).ToList()
        BindGrid(orders)
    End If
End Sub

Protected Sub OnSearch(ByVal sender As Object, ByVal e As EventArgs)
    Dim entities As NORTHWINDEntities = New NORTHWINDEntities()
    Dim orders As List(Of Order) = entities.Orders.Take(10).ToList()

    If Not String.IsNullOrEmpty(txtSearch.Text.Trim()) Then
        orders = orders.Where(Function(x) x.ShipCountry = txtSearch.Text.Trim()).ToList()
    End If

    BindGrid(orders)
End Sub

Private Sub BindGrid(ByVal orders As List(Of Order))
    gvOrders.DataSource = orders
    gvOrders.DataBind()
End Sub

Screenshot