using (IDbConnection db = new SqlConnection(ConfigurationManager.ConnectionStrings["myDbConnection"].ConnectionString))
{
    string insertQuery = @"INSERT INTO [dbo].[Customer]([FirstName], [LastName], [State], [City], [IsActive], [CreatedOn]) VALUES (@FirstName, @LastName, @State, @City, @IsActive, @CreatedOn)";

    var result = db.Execute(insertQuery, new
    {
        customerModel.FirstName,
        customerModel.LastName,
        StateModel.State,
        CityModel.City,
        isActive,
        CreatedOn = DateTime.Now
    });
}