ASP.Net: Handle Null value in DataRow using C#

I have below code. I have null value in itemrate(Rate), so how it will be handle.

C#

Code

DataTable dt = (DataTable)ViewState["dt"];
int codeitem, orderqty;
decimal itemrate;
foreach (DataRow row in dt.Rows)
{
    orderqty = int.Parse(row["orderqty"].ToString());
    codeitem = int.Parse(row["Codeitem"].ToString());
    itemrate = decimal.Parse(row["Rate"].ToString());
    this.InsertRows(codeitem, orderqty, itemrate);
}

Input string was not in a correct format.

itemrate = decimal.Parse(row["Rate"].ToString());