Inserting into LocalDB Visual Studio 2012

Question

I have a problem that I couldn't find a solution to it, which is inserting data to LocalDB in Visual Studio Windows Form App - C# Actually, I'm using a Class Library, and I added a reference to it in my Windows Form app The problem is when I want to add new data to the local db, it doesn't show any errors, however, I see no data inserted into the database

This is my code in the Class Library, which is a general method the could be used to add any data to any table in the database

    public virtual void Add(Item item)
    {
        int count = 0;
        //create the first part of the Add SQL string
        string addString = "INSERT INTO " + table + "(";

        //add each field name from Item UpdateFields to the string
        foreach (KeyValuePair<string, string> field in item.UpdateFields)
        {
            addString += "[" + field.Key + "]";
            count++;
            //add a comma when end of UpdateFields collection is reached
            if (count < item.UpdateFields.Count)
            { addString += ", "; }

        }

        //start second part of Add string
        addString += ") VALUES(";
        count = 0;
        //add each value from Item UpdateFields to the string
        foreach (KeyValuePair<string, string> field in item.UpdateFields)
        {
            if (field.Value != null)
            { addString += "'" + field.Value.ToString() + "'"; }
            else
            { addString += "NULL"; }
            count++;
            //add a comma when end of UpdateFields collection is reached
            if (count < item.UpdateFields.Count)
            { addString += ", "; }
        }
        //add bracket at end of Add string
        addString += ")";

        command.CommandText = addString;

        try
        {
            command.ExecuteNonQuery();
        }
        catch (SqlException ex)
        {
            item.Valid = false;
            item.ErrorMessage = ex.Message;
        }


    }

and here where I'm using it to add an Account information

cc = new Account(accountID);
acc.UserName = userNametxt.Text;
acc.Password = "P@ssword";
acc.Email = emailtxt.Text;
acc.CreatedBy = "";
acc.Status = "1";
acc.LastLoginDateTime = null;
acc.LastFailureLoginDateTime = null;
accounts.Add(acc);
if (!acc.Valid)
{
  MessageBox.Show(acc.ErrorMessage);
}
else
{
  MessageBox.Show("Account has been added successfully!!");
}

and the following is my string connection

new SqlConnection(Properties.Settings.Default.TestConnectionString);  

Thanks in advance