How to get the changed value in Input Text?

Use input change event to get the changed value in onchange event argument. If you bind using the two-way bind to value property, it will automatically change the value into the Value property.

<input placeholder="Enter your text" @onchange="@onChange" />

@code {

    private string value { get; set; }
    private void onChange(Microsoft.AspNetCore.Components.ChangeEventArgs args)
    {
        value = (string)args.Value;
    }
}

or

<input placeholder="Enter your text" @bind-value="@value" />

@code {

    private string value { get; set; }
}