c# - String was not recognized as a valid DateTime -

my code is:

 protected void page_load(object sender, eventargs e)     {         string mydate = request.querystring["period"];         if (!string.isnullorempty(mydate))         {             mydate = mydate.replace("!", ":");         }         datetime dt1 = convert.todatetime(mydate);         datetime dt2 = datetime.now;         timespan variable = dt2 - dt1;         if (variable.totalminutes > 5)         {             response.write("download time expired now");         }         else         {             response.redirect("default.aspx", false);         }        } 

and i'm getting error like:

string not recognized valid datetime.

try datetime.parseexact() method;

converts specified string representation of date , time datetime equivalent using specified format , culture-specific format information. the format of string representation must match specified format exactly.

datetime date = datetime.parseexact(mydate, "dd/mm/yyyy hh:mm:ss tt", cultureinfo.invariantculture); 

here demo.

you can check more custom date formats custom date , time format strings