Checking that a number falls in range

A range validator checks that a value sits between a lower and an upper limit. It is the right tool for quantities, ages and dates.

Setting the limits

<asp:TextBox id="txtQty" runat="server" />
<asp:RangeValidator
    ControlToValidate="txtQty"
    MinimumValue="1"
    MaximumValue="20"
    Type="Integer"
    ErrorMessage="Choose between 1 and 20"
    runat="server" />

Two things people forget

• Set the type, or the validator compares the value as text and the result surprises you.
• Decide whether the limits themselves are allowed, because the comparison can include or exclude them.

When the rule is a shape rather than a range, use the pattern validator.