Checking the database value null

[PPCC]

if (OrderLinesDs.Tables[0].Rows[0]["Billing_FAX"]!=null)
{
txtFax.Text="";
}
else
{
txtFax.Text=(string)OrderLinesDs.Tables[0].Rows[0]["Billing_FAX"];
}
>>above code checking both the condition.what is the best solutions on this

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