<TelerikNumericTextBox @bind-Value="@ActiveTabIndex" Min="-1" Max="2" />

<TelerikTabStrip @bind-ActiveTabIndex="@ActiveTabIndex">
    <TabStripTab Title="First">
        First tab content.
    </TabStripTab>
    <TabStripTab Title="Second">
        Second tab content. I will be active initially due to the default value of the parameter.
        <br />
        <TelerikButton OnClick="@SelectThirdTab">Select Third Tab</TelerikButton>
    </TabStripTab>
    <TabStripTab Title="Third">
        Third tab content.
    </TabStripTab>
</TelerikTabStrip>

@code {
    public int ActiveTabIndex { get; set; } = -1;

    void SelectThirdTab()
    {
        ActiveTabIndex = 2;
    }
}