Hey Omega,

Please refer below sample.

Filter DataTable (DataSet) using LINQ in ASP.Net, C# and VB.Net

HTML

CustomerId :
<asp:TextBox runat="server" ID="txtId" /><br />
<asp:Button Text="Search" runat="server" OnClick="Search" />
<asp:GridView runat="server" ID="gvEmployees" AutoGenerateColumns="true">
</asp:GridView>

Namespaces

C#

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

VB.Net

Imports System.Data.SqlClient
Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = GetData();
        gvEmployees.DataSource = dt;
        gvEmployees.DataBind();
    }
}

private static DataTable GetData()
{
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand("Select * from Customers", con))
        {
            using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
            {
                using (DataTable dt = new DataTable())
                {
                    adapter.Fill(dt);
                    return dt;
                }
            }
        }
    }
}

protected void Search(object sender, EventArgs e)
{
    using (DataTable dt = GetData())
    {
        DataTable customers = (from customer in dt.AsEnumerable()
                                where customer.Field<int>("CustomerId") >= Convert.ToInt32(txtId.Text)
                                select customer).CopyToDataTable();
        gvEmployees.DataSource = customers;
        gvEmployees.DataBind();
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As DataTable = GetData()
        gvEmployees.DataSource = dt
        gvEmployees.DataBind()
    End If
End Sub

Private Shared Function GetData() As DataTable
    Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("constr").ConnectionString)
        Using cmd As SqlCommand = New SqlCommand("Select * from Customers", con)
            Using adapter As SqlDataAdapter = New SqlDataAdapter(cmd)
                Using dt As DataTable = New DataTable()
                    adapter.Fill(dt)
                    Return dt
                End Using
            End Using
        End Using
    End Using
End Function

Protected Sub Search(ByVal sender As Object, ByVal e As EventArgs)
    Using dt As DataTable = GetData()
        Dim customers As DataTable = (From customer In dt.AsEnumerable() Where customer.Field(Of Integer)("CustomerId") >= Convert.ToInt32(txtId.Text) Select customer).CopyToDataTable()
        gvEmployees.DataSource = customers
        gvEmployees.DataBind()
    End Using
End Sub

Screenshot