Retain ASP.Net GridView filter on Sorting and paging using C# and VB.Net

Hi roon3y,

Please refer below sample.

HTML

City :
<asp:DropDownList ID="ddlCity" AppendDataBoundItems="true" runat="server">
    <asp:ListItem Text="Select" Value="0" />
</asp:DropDownList>
Country:
<asp:DropDownList ID="ddlCountry" AppendDataBoundItems="true" runat="server">
    <asp:ListItem Text="Select" Value="0" />
</asp:DropDownList>
<asp:Button ID="btnSearch" runat="server" OnClick="Search" Text="Search" />
<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false" AllowPaging="true"
    AllowSorting="true" OnSorting="OnSorting" OnPageIndexChanging="OnPageIndexChanging"
    PageSize="2">
    <Columns>
        <asp:TemplateField HeaderText="CustomerID" SortExpression="CustomerID">
            <ItemTemplate>
                <%# Eval("CustomerID")%>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="ContactName" HeaderText="ContactName" SortExpression="ContactName" />
        <asp:BoundField DataField="City" HeaderText="City" SortExpression="City" />
        <asp:BoundField DataField="Country" HeaderText="Country" SortExpression="Country" />
    </Columns>
</asp:GridView>

Namespace

C#

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

VB.Net

Imports System.Data.SqlClient
Imports System.Data

Code

C#

private string SortDirection
{
    get { return ViewState["SortDirection"] != null ? ViewState["SortDirection"].ToString() : "ASC"; }
    set { ViewState["SortDirection"] = value; }
}
protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.BindGrid();
    }
}

private void BindGrid(string sortExpression = null, string searchCity = null, string searchCountry = null)
{
    string query = "SELECT CustomerId, ContactName, City, Country FROM Customers";
    string constr = ConfigurationManager.ConnectionStrings["Constring"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand())
        {
            if (!string.IsNullOrEmpty(searchCity) && !string.IsNullOrEmpty(searchCountry))
            {
                query += " WHERE City = @City AND Country=@Country ";
                cmd.Parameters.AddWithValue("@City", searchCity);
                cmd.Parameters.AddWithValue("@Country", searchCountry);
            }
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.CommandText = query;
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    if (sortExpression != null)
                    {
                        DataView dv = dt.AsDataView();
                        this.SortDirection = this.SortDirection == "ASC" ? "DESC" : "ASC";

                        dv.Sort = sortExpression + " " + this.SortDirection;
                        this.gvCustomers.DataSource = dv;
                    }
                    else
                    {
                        ddlCity.DataSource = dt;
                        ddlCountry.DataSource = dt;
                        this.gvCustomers.DataSource = dt;
                        ddlCity.DataValueField = "City";
                        ddlCity.DataTextField = "City";
                        ddlCountry.DataValueField = "Country";
                        ddlCountry.DataTextField = "Country";
                    }
                    ddlCity.DataBind();
                    ddlCountry.DataBind();
                    this.gvCustomers.DataBind();
                }
            }
        }
    }
}

protected void Search(object sender, EventArgs e)
{
    this.BindGrid(null, ddlCity.SelectedItem.Value, ddlCountry.SelectedItem.Value);
}

protected void OnPageIndexChanging(object sender, GridViewPageEventArgs e)
{
    this.gvCustomers.PageIndex = e.NewPageIndex;
    this.BindGrid(null, ddlCity.SelectedItem.Value, ddlCountry.SelectedItem.Value);
}

protected void OnSorting(object sender, GridViewSortEventArgs e)
{
    this.BindGrid(e.SortExpression, ddlCity.SelectedItem.Value, ddlCountry.SelectedItem.Value);
}

VB.Net

Private Property SortDirection As String
    Get
        Return If(ViewState("SortDirection") IsNot Nothing, ViewState("SortDirection").ToString(), "ASC")
    End Get
    Set(ByVal value As String)
        ViewState("SortDirection") = value
    End Set
End Property

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If Not Me.IsPostBack Then
        Me.BindGrid()
    End If
End Sub

Private Sub BindGrid(Optional ByVal sortExpression As String = Nothing, Optional ByVal searchCity As String = Nothing, Optional ByVal searchCountry As String = Nothing)
    Dim query As String = "SELECT CustomerId, ContactName, City, Country FROM Customers"
    Dim constr As String = ConfigurationManager.ConnectionStrings("Constring").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Using cmd As SqlCommand = New SqlCommand()
            If Not String.IsNullOrEmpty(searchCity) AndAlso Not String.IsNullOrEmpty(searchCountry) Then
                query += " WHERE City = @City AND Country=@Country "
                cmd.Parameters.AddWithValue("@City", searchCity)
                cmd.Parameters.AddWithValue("@Country", searchCountry)
            End If
            Using sda As SqlDataAdapter = New SqlDataAdapter()
                cmd.CommandText = query
                cmd.Connection = con
                sda.SelectCommand = cmd

                Using dt As DataTable = New DataTable()
                    sda.Fill(dt)
                    If sortExpression IsNot Nothing Then
                        Dim dv As DataView = dt.AsDataView()
                        Me.SortDirection = If(Me.SortDirection = "ASC", "DESC", "ASC")
                        dv.Sort = sortExpression & " " & Me.SortDirection
                        Me.gvCustomers.DataSource = dv
                    Else
                        ddlCity.DataSource = dt
                        ddlCountry.DataSource = dt
                        Me.gvCustomers.DataSource = dt
                        ddlCity.DataValueField = "City"
                        ddlCity.DataTextField = "City"
                        ddlCountry.DataValueField = "Country"
                        ddlCountry.DataTextField = "Country"
                    End If
                    ddlCity.DataBind()
                    ddlCountry.DataBind()
                    Me.gvCustomers.DataBind()
                End Using
            End Using
        End Using
    End Using
End Sub

Protected Sub Search(ByVal sender As Object, ByVal e As EventArgs)
    Me.BindGrid(Nothing, ddlCity.SelectedItem.Value, ddlCountry.SelectedItem.Value)
End Sub

Protected Sub OnPageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)
    Me.gvCustomers.PageIndex = e.NewPageIndex
    Me.BindGrid(Nothing, ddlCity.SelectedItem.Value, ddlCountry.SelectedItem.Value)
End Sub

Protected Sub OnSorting(ByVal sender As Object, ByVal e As GridViewSortEventArgs)
    Me.BindGrid(e.SortExpression, ddlCity.SelectedItem.Value, ddlCountry.SelectedItem.Value)
End Sub

Screenshot