VB.NET appropriate replacement for VB6.Format(field, formatStyle)?

As the title says, how can I achieve this in VB.NET without using VB6 compatibility library?

Code:

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maskedTextBox.Text = VB6.Format(maskedTextBox.Text, "###000")

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i.e add leading zeroes?

If you want to add leading zeroes - leading any characters - to a String then you call its PadLeft method.