Stop (Prevent) duplicate record insert into database in ASP.Net using C# and VB.Net

Hi Akhter,

Please refer below sample.

Database

I have made use of the following table Customers with the schema as follows.

I have already inserted few records in the table.

You can download the database table SQL by clicking the download link below.

Download SQL file

Procedure

CREATE PROCEDURE [dbo].[Customers_InsertCustomer]
	@Name VARCHAR (100),
	@Country VARCHAR (100)
AS 
BEGIN
	IF NOT EXISTS(SELECT CustomerId FROM Customers WHERE Name = @Name AND Country = @Country)
	BEGIN
		INSERT INTO Customers (Name, Country) 
		VALUES (@Name, @Country)
	END
END

HTML

<table>
    <tr>
        <td>Name:</td>
        <td><asp:TextBox runat="server" ID="txtName" /></td>
    </tr>
    <tr>
        <td>Country:</td>
        <td><asp:TextBox runat="server" ID="txtCountry" /></td>
    </tr>
    <tr>
        <td><asp:Button ID="btnAdd" Text="Add" runat="server" OnClick="Add" /></td>
    </tr>
</table>
<br />
<asp:GridView runat="server" ID="gvCustomers" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="Name" HeaderText="Name" />
        <asp:BoundField DataField="Country" HeaderText="Country" />
    </Columns>
</asp:GridView>

Namespaces

C#

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

VB.Net

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration

Code

C#

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

protected void Add(object sender, EventArgs e)
{
    int recordsInserted = 0;
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlCommand cmd = new SqlCommand("Customers_InsertCustomer"))
        {
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Connection = con;
            cmd.Parameters.AddWithValue("@Name", txtName.Text);
            cmd.Parameters.AddWithValue("@Country", txtCountry.Text);
            con.Open();
            recordsInserted = cmd.ExecuteNonQuery();
            con.Close();
        }
    }

    this.BindGrid();

    if (recordsInserted == -1)
    {
        ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Data already exists.');", true);
    }
}

private void BindGrid()
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT Name, Country FROM Customers", con))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    gvCustomers.DataSource = dt;
                    gvCustomers.DataBind();
                }
            }
        }
    }
}

VB.Net

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

Protected Sub Add(ByVal sender As Object, ByVal e As EventArgs)
    Dim recordsInserted As Integer = 0
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(conString)
        Using cmd As SqlCommand = New SqlCommand("Customers_InsertCustomer")
            cmd.CommandType = CommandType.StoredProcedure
            cmd.Connection = con
            cmd.Parameters.AddWithValue("@Name", txtName.Text)
            cmd.Parameters.AddWithValue("@Country", txtCountry.Text)
            con.Open()
            recordsInserted = cmd.ExecuteNonQuery()
            con.Close()
        End Using
    End Using

    Me.BindGrid()

    If recordsInserted = -1 Then
        ClientScript.RegisterStartupScript(Me.GetType(), "alert", "alert('Data already exists.');", True)
    End If
End Sub

Private Sub BindGrid()
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(conString)
        Using cmd As SqlCommand = New SqlCommand("SELECT Name, Country FROM Customers", con)
            Using sda As SqlDataAdapter = New SqlDataAdapter(cmd)
                Using dt As DataTable = New DataTable()
                    sda.Fill(dt)
                    gvCustomers.DataSource = dt
                    gvCustomers.DataBind()
                End Using
            End Using
        End Using
    End Using
End Sub

Screenshot