Compare and validate string with another string using C# and VB.Net in ASP.Net

Hi nagaraju60,

Refer below sample.

HTML

Name :
<asp:TextBox runat="server" ID="txtName" />
<br />
<asp:Button Text="Submit" runat="server" OnClick="Submit" />

Namespaces

C#

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

VB.Net

Imports System.Data.SqlClient

Code

C#

protected void Submit(object sender, EventArgs e)
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        SqlCommand cmd = new SqlCommand("SELECT Cust_Nm FROM tblCheckData WHERE Cust_Nm = @Name", con);
        cmd.Parameters.AddWithValue("@Name", txtName.Text.Replace("..", ".").Replace("  ", " "));
        con.Open();
        string name = Convert.ToString(cmd.ExecuteScalar());
        if (string.IsNullOrEmpty(name))
        {
            cmd = new SqlCommand("INSERT INTO tblCheckData VALUES(@Name)", con);
            cmd.Parameters.AddWithValue("@Name", txtName.Text.Replace("..", ".").Replace("  ", " "));
            cmd.ExecuteNonQuery();
        }
        else
        {
            con.Close();
            ScriptManager.RegisterStartupScript(this, this.GetType(), "Message", "alert('Name already exist');", true);
        }
    }
}

VB.Net

Protected Sub Submit(ByVal sender As Object, ByVal e As EventArgs)
    Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Dim cmd As SqlCommand = New SqlCommand("SELECT Cust_Nm FROM tblCheckData WHERE Cust_Nm = @Name", con)
        cmd.Parameters.AddWithValue("@Name", txtName.Text.Replace("..", ".").Replace("  ", " "))
        con.Open()
        Dim name As String = Convert.ToString(cmd.ExecuteScalar())

        If String.IsNullOrEmpty(name) Then
            cmd = New SqlCommand("INSERT INTO tblCheckData VALUES(@Name)", con)
            cmd.Parameters.AddWithValue("@Name", txtName.Text.Replace("..", ".").Replace("  ", " "))
            cmd.ExecuteNonQuery()
        Else
            con.Close()
            ScriptManager.RegisterStartupScript(Me, Me.GetType(), "Message", "alert('Name already exist');", True)
        End If
    End Using
End Sub

Screenshot