Insert distinct record using LINQ query in ASP.Net using C# and VB.Net

Hi nauna,

Please refer below sample.

HTML 

<asp:Button Text="Save" ID="btnSave" OnClick="Save" runat="server" />

Namespaces

C#

using System.Data;

VB.Net

Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.GetDataTable();
    }
}

protected void Save(object sender, EventArgs e)
{
    int id = 2;
    string name = "Mudassar Khan";
    string country = "India";
    DataTable dt = GetDataTable();
    var duplicate = from d in dt.AsEnumerable()
                    where d.Field<int>("Id") == id
                    && d.Field<string>("Name") == name
                    && d.Field<string>("Country") == country
                    select d;
    if (duplicate.Count() > 0)
    {
        ClientScript.RegisterStartupScript(this.GetType(), "message", "alert('Record already exist')", true);
    }

    else
    {
        dt.Rows.Add(id, name, country);
    }
}

private DataTable GetDataTable()
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[3] {
                        new DataColumn("Id", typeof(int)),
                        new DataColumn("Name", typeof(string)),
                        new DataColumn("Country",typeof(string))});

    dt.Rows.Add(1, "John Hammond", "United States");
    dt.Rows.Add(2, "Mudassar Khan", "India");
    dt.Rows.Add(3, "Suzanne Mathews", "France");
    dt.Rows.Add(4, "Robert Schidner", "Russia");
    return dt;
}

VB.Net 

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

Protected Sub Save(ByVal sender As Object, ByVal e As EventArgs)
    Dim id As Integer = 2
    Dim name As String = "Mudassar Khan"
    Dim country As String = "India"
    Dim dt As DataTable = GetDataTable()
    Dim duplicate = From d In dt.AsEnumerable() Where d.Field(Of Integer)("Id") = id AndAlso d.Field(Of String)("Name") = name AndAlso d.Field(Of String)("Country") = country Select d

    If duplicate.Count() > 0 Then
        ClientScript.RegisterStartupScript(Me.GetType(), "message", "alert('Record already exist')", True)
    Else
        dt.Rows.Add(id, name, country)
    End If
End Sub

Private Function GetDataTable() As DataTable
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn(2) {New DataColumn("Id", GetType(Integer)), New DataColumn("Name", GetType(String)), New DataColumn("Country", GetType(String))})
    dt.Rows.Add(1, "John Hammond", "United States")
    dt.Rows.Add(2, "Mudassar Khan", "India")
    dt.Rows.Add(3, "Suzanne Mathews", "France")
    dt.Rows.Add(4, "Robert Schidner", "Russia")
    Return dt
End Function