When the mode of the text box is set to multiple rows, the maxlength attribute is invalid. You can use the regularexpressionvalidator control,CodeAs follows:
Code
< ASP: textbox ID = "Txtintroduct" Runat = "Server" Textmode = "Multiline"
Height = "120px" Width = "240px" Class = "Input_text" />
< ASP: regularexpressionvalidator ID = "Regularexpressionvalidator2" Controltovalidate = "Txtintroduct"
Validationexpression = "([^.] |.) {0,300 }" Runat = "Server" Setfocusonerror = "True" Display = "NONE"
Validationgroup = "Addapply" Errormessage = "Simple introduction, less than 300 words! " > </ ASP: regularexpressionvalidator >
< C0: validatorcalloutextender ID = "Validatorcalloutextender11" Highlightcssclass = "Validatorcallouthighlight"
Runat = "Server" Enabled = "True" Targetcontrolid = "Regularexpressionvalidator2" >
</ C0: validatorcalloutextender >