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You can make use of one of the KeyDown/KeyUp/KeyPress events which enables you to check the pressed key before it is printed to the component.<br />
<br />
procedure TForm1.Edit1KeyPress(Sende<wbr />r: TObject; var Key: Char);<br />
begin<br />
&nbsp; if Key in ['a'..'z', 'A'..'Z','\', ..etc] &nbsp;// List all the allowed Char ranges<br />
&nbsp; if not TPath.HasValidFileNameChar<wbr />s(Edit1.Te<wbr />xt+Key, ...) // Or check the key if is not valid just reset the key<br />
&nbsp; &nbsp; Key:= #0;<br />
end;
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You can make use of one of the KeyDown/KeyUp/KeyPress events which enables you to check the pressed key before it is printed to the component.

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
  if Key in ['a'..'z', 'A'..'Z','\', ..etc]  // List all the allowed Char ranges
  if not TPath.HasValidFileNameChars(Edit1.Text+Key, ...) // Or check the key if is not valid just reset the key
    Key:= #0;
end;

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This is not reliable, as one can paste still PASTE chars which are not allowed as filename.
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This is not reliable, as one can paste still PASTE chars which are not allowed as filename.

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Hi! In a Delphi XE7 VCL application, at runtime I need to validate the text input inside a <b>TEdit</b> to allow only valid file name characters. In Delphi XE7 there is the <b>System.IOUtils.TPath.HasVa<wbr />lidFileNam<wbr />eChars</b> function. How can this be applied in real-time in a <b>TEdit</b> component?<br />
<br />
Unfortunately, the <b>TEdit</b> component has no <b>OnValidating</b> event. <u>I don't want to use the <b>OnChange</b> event</u>, because it looks ugly when the character appears for a short time. The validation must occur BEFORE the character appears.
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Hi! In a Delphi XE7 VCL application, at runtime I need to validate the text input inside a TEdit to allow only valid file name characters. In Delphi XE7 there is the System.IOUtils.TPath.HasValidFileNameChars function. How can this be applied in real-time in a TEdit component?

Unfortunately, the TEdit component has no OnValidating event. I don't want to use the OnChange event, because it looks ugly when the character appears for a short time. The validation must occur BEFORE the character appears.

Validate TEdit to allow only valid file name characters?

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