In this article I will explain with an example, how to filter DataTable (DataSet) based on Column value using LINQ in ASP.Net, C# and VB.Net.
Actually it’s the DataTable inside the DataSet which can be filtered based on Column value using the LINQ WHERE clause in C# and VB.Net and hence this article is applicable for both DataTables and DataSets.
 
 

Database

I have made use of the following table Customers with the schema as follows.
Filter DataTable (DataSet) using LINQ in ASP.Net, C# and VB.Net
 
I have already inserted few records in the table.
Filter DataTable (DataSet) using LINQ in ASP.Net, C# and VB.Net
 
Note: You can download the database table SQL by clicking the download link below.
          Download SQL file
 
 

HTML Markup

The following HTML Markup consists of:
DropDownList – For selecting Country and it is assigned with OnSelectedIndexChanged property.
GridView - For displaying data.
The GridView consists of three BoundField columns.
Country:
<asp:DropDownList ID="ddlCountry" runat="server" AutoPostBack="true" OnSelectedIndexChanged="Country_Changed">
    <asp:ListItem Text="" Value=""></asp:ListItem>
    <asp:ListItem Text="United States" Value="United States"></asp:ListItem>
    <asp:ListItem Text="India" Value="India"></asp:ListItem>
    <asp:ListItem Text="France" Value="France"></asp:ListItem>
    <asp:ListItem Text="Russia" Value="Russia"></asp:ListItem>
</asp:DropDownList>
<hr />
<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="CustomerId" HeaderText="Customer Id" />
        <asp:BoundField DataField="Name" HeaderText="Name" />
        <asp:BoundField DataField="Country" HeaderText="Country" />
    </Columns>
</asp:GridView>
 
 

Namespaces

You will need to import the following namespaces.
C#
using System.Data;
using System.Linq;
using System.Configuration;
using System.Data.SqlClient;
 
VB.Net
Imports System.Data
Imports System.Linq
Imports System.Configuration
Imports System.Data.SqlClient
 
 

Filter DataTable based on Column value using LINQ

A function named GetData is used to fetch the records from the Customers table and return them in the form of a DataTable.
The GetData function is called at two places, first inside the Page_Load event of the page and second inside the Country_Changed event handler which is triggered on the DropDownList SelectedIndexChanged event.
Inside the Country_Changed event handler, first the selected value of the Country is fetched from the DropDownList.
If the selected value is not empty, then DataTable records are filtered using the WHERE clause of LINQ and the results are used to populate the GridView control.
If the selected value is empty, then simply the DataTable is used to populate the GridView control.
C#
protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = this.GetData();
        gvCustomers.DataSource = dt;
        gvCustomers.DataBind();
    }
}
 
protected void Country_Changed(object sender, EventArgs e)
{
    string country = ddlCountry.SelectedItem.Value;
    DataTable dt = this.GetData();
    if (!string.IsNullOrEmpty(country))
    {
        var customers = from customer in dt.AsEnumerable()
                        where customer.Field<string>("Country") == country
                        select new
                        {
                             CustomerId = customer.Field<int>("CustomerId"),
                             Name = customer.Field<string>("Name"),
                             Country = customer.Field<string>("Country")
                        };
        gvCustomers.DataSource = customers;
        gvCustomers.DataBind();
    }
    else
    {
        gvCustomers.DataSource = dt;
        gvCustomers.DataBind();
    }
}
 
private DataTable GetData()
{
    DataTable dt = new DataTable();
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    string sql = "SELECT * FROM Customers";
    using (SqlConnection conn = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand(sql))
        {
            cmd.Connection = conn;
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                sda.Fill(dt);
            }
        }
    }
 
    return dt;
}
 
VB.Net
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As DataTable = Me.GetData()
        gvCustomers.DataSource = dt
        gvCustomers.DataBind()
    End If
End Sub
 
Protected Sub Country_Changed(sender As Object, e As EventArgs)
    Dim country As String = ddlCountry.SelectedItem.Value
    Dim dt As DataTable = Me.GetData()
    Dim dataView As DataView = dt.DefaultView
    If Not String.IsNullOrEmpty(country)Then
        Dim customers = dt.AsEnumerable().Select(Function(customer)New With {
            .CustomerId = customer.Field(Of Integer)("CustomerId"),
            .Name = customer.Field(Of String)("Name"),
            .Country = customer.Field(Of String)("Country")
        }).Where(Function(customer) customer.Country = country)
        gvCustomers.DataSource = customers
        gvCustomers.DataBind()
    Else
        gvCustomers.DataSource = dt
        gvCustomers.DataBind()
    End If
End Sub
 
Private Function GetData() As DataTable
    Dim dt As New DataTable()
    Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Dim sql As String = "SELECT * FROM Customers"
    Using conn As New SqlConnection(constr)
        Using cmd As New SqlCommand(sql)
            cmd.Connection = conn
            Using sda As New SqlDataAdapter(cmd)
                sda.Fill(dt)
            End Using
        End Using
    End Using
 
    Return dt
End Function
 
 

Screenshot

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

Demo

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Downloads

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