how to pass null value to text box with DateTime Data

Question

Hi,

   I am passing Date as "04/15/2014" on click of Calender Selected Change to text box. In my Code behind File i am making

if(txtDate.text=="")

{

   value=

//I am not getting what to assign

}

else

{

  value=DatetTime.Parse(txtDate.text);

//This is giving error as "Error: Sys.WebForms.PageRequestManagerServerErrorException: The string was not recognized as a valid DateTime. There is a unknown word starting at index 0."

}

 

please help me with this issue.

Regards,

Sivapratap