An "error provider" is simply a
DotNet object that can be associated with an
individual control. When you set its error message property, it suddenly
become visible as a little red circle next to the control (you can set the
icon to be whatever you choose), and it has a tool tip that displays the
error message.
--
MikeStallings (on behalf of
FormValidation)
BTW, these are typically called 'Server Validators' (or just 'Validators'), at least as of .NET 1.0 RTM. (I didn't participate in the original beta - maybe they were "error providers" back then?) At least, they're called so in the context of ASP.NET - I think validation exists in Windows Forms, but I haven't worked with it.
Server Validators validate the content of that object (the validator is itself a .NET server control with a C
ontrolToValidate property, which you set to the control-you-wish-to-validate's ID property). Examples include a R
equiredFieldValidator (value of control can't be empty), C
ompareValidator (compares the value to another control, e.g. comparing the 'password' and 'repeat password' fields), and R
egularExpressionValidator (naturally, validates the content of a control via regular expression). There are several more, and you can inherit from B
aseValidator to code your own. Typically these are used to validate T
extBox controls, but any control marked with the V
alidationPropertyAttribute (which specifies the public property of that control that should be validated) can be used in the C
ontrolToValidate property of a validator.
Reference:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemwebuiwebcontrolsbasevalidatorclasstopic.asp
--
JosephRiesen