Hi Cemil,
Greetings from Syncfusion support,
We have validated your reported query. Currently, we couldn’t wrap the built-in dialog buttons inside the EditForm that placed in the content. You can achieve form validation, by placing the form inside the <ChildContent> tags and render buttons wrapped inside the SfDialog, with the footer element class <div class="e-footer-content"> to perform the form validation. The SfDialog can be prevented from closing or submitted based form validation. We have also prepared a sample that tries to meet your requirements.
Please let us know if the solution helps,
Regards,
Indrajith