Date format in RangeValidator

I am using RangeValidator to validate date enter in textbox and its working fine with default date format but now i want the date format in "dd/MM/yyy" but its generating excption with this date format. please provide me solution my code:

in aspx page:

<asp:TextBox ID="txtrequiredby" runat="server" ></asp:TextBox >
<cc1:CalendarExtender ID="txtrequiredby_CalendarExtender" Format="dd/MM/yyyy"
runat="server" Enabled="True" TargetControlID="txtrequiredby" >
</cc1:CalendarExtender >

 <asp:RangeValidator ID="rvreqby" runat="server" ErrorMessage="Required By Date
Greater Than or Equal to current date" ControlToValidate="txtrequiredby" 
 Display="Dynamic" Type="Date" ></asp:RangeValidator >

in codebehind:

rvreqby.MinimumValue = clsGeneral.FromSqlDate( DateTime.Now);
rvreqby.Maxi开发者_如何转开发mumValue = clsGeneral.FromSqlDate( DateTime.Now.AddYears(200));

public static string  FromSqlDate(DateTime  date)
{
   return date.ToString("dd/MM/yyyy");
}

MinimumValue & MaximumValue need to be set in the Page_PreRender event and appear to require the date format as "dd-MM-yy"...see last post on Rangevalidator Min Max Value error

protected void Page_PreRender(object sender, EventArgs e)
{
    RangeValidator1.MinimumValue = DateTime.Now.Date.ToString("dd-MM-yy");
    RangeValidator1.MaximumValue = DateTime.Now.Date.AddYears(90).ToString("dd-MM-yy");
}

Format of the MinimumValue and MaximumValue should be yyyy/MM/dd

Check documentation here: https://msdn.microsoft.com/en-us/library/ydez7ad7(v=vs.110).aspx