The <RegExpErrorMessage> tag works with the <RegExp> tag, outputting a customizable error message when regular expression validation fails on a string in an Employee Property Grid.
If the validation fails, the field is tagged on-screen, and your error message pops up when the user hovers over the field. If you use a <RegExp> tag without a <RegExpErrorMessage> tag, a standard error message displays: "[Field name]: field value does not match given Regex".
The following sample restricts a field to five lowercase letters, and outputs the custom error message "Only up to 5 lowercase letters are allowed":
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<EPGridColumn>
<BindingProperty>Value</BindingProperty>
<XRefCode>EmployeePropertyXrefCode21</XRefCode>
<IsRequired>True</IsRequired>
<TextAlignment>Right</TextAlignment>
<DefaultValue>az05</DefaultValue>
<RegExp>^[a-z]{0,5}$</RegExp>
<RegExpErrorMessage>Only up to 5 lowercase letters are allowed</RegExpErrorMessage>
</EPGridColumn>