How do not allow FreeTextBox content with full of space characters?

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C#

I have a FreeTextBox FTB in my aspx page.



<asp:ValidationSummary ID="Alert" runat="server" CssClass="failureNotification" HeaderText=""/>

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="FTB" ErrorMessage=" Content cannot be empty"></asp:RequiredFieldValidator>

I've used RequiredFieldValidator before for `TextBox` control.

Now I use it for FreeTextbox control. It works fine if I let the FreeTextBox empty, but I doent show the ErrorMessage when the FreeTextBox is full of space character.

As recommended, I use RegularExpressionValidator

<asp:RegularExpressionValidator ID="rev" runat="server" ControlToValidate="FTB" ErrorMessage="Content cannot be only space character" ValidationExpression="[^\s]+"/>

But the RegularExpressionValidator is deny any space character in the text (space between words).
I just only want to not allow the text which has full of space characters.

Help!!!