[Solved] Convert to Decimal Error: Input string was not in a correct format

When i am inserting decimal value into database from GridView then below error is coming.

Input string was not in a correct format.

decimal b_rate = Convert.ToDecimal(row.Cells[7].ToString());

value is 0.5428

protected void btn_Save_Click(object sender, EventArgs e)
{
    foreach (GridViewRow row in GVballist.Rows)
    {
        if ((row.FindControl("chkRows") as CheckBox).Checked)
        {
            string Id = row.Cells[2].Text;
            decimal b_rate = Convert.ToDecimal(row.Cells[7].ToString());

            this.Insert(Id, b_rate);
        }
    }

}
private void Insert(string Id, decimal b_rate)
{
    using (SqlCommand cmd = new SqlCommand("[Sp_Update_BBINVOICE]", con))
    {

        cmd.CommandType = CommandType.StoredProcedure;


        cmd.Parameters.AddWithValue("@DID", Id);
        cmd.Parameters.AddWithValue("@B_Rate", b_rate);
        cmd.Parameters.AddWithValue("@CustomerID", DDLcus.SelectedValue);
        con.Open();
        cmd.ExecuteNonQuery();
        ScriptManager.RegisterStartupScript(this, this.GetType(), "alert", " alert('Pack saved sucessfully');", true);
        con.Close();
    }
}