Disabled the radiobutton

I use radiobutton with Null as initial value.
I would like to know if it's possible to disable Value2 after to have selected the Value 1 and the Value 1 will remain enabled (or disabled)

 int? nullableValue = null;
 <RadzenRadioButtonList @bind-Value=@nullableValue TValue="int?" >
                                                <RadzenRadioButtonListItem Text="A" Value="1" TValue="int?" />
                                                <RadzenRadioButtonListItem Text="B" Value="2" TValue="int?" />
                                                   @if (nullableValue == 1) { dev.DTb = "NP"; dev.DI = "Select..."; dev.BlSAQ = "Select..."; }
                                                    else if (nullableValue == 2) { dev.DTb = "Select.."; dev.DI = "NP"; dev.BlSAQ = "Select...";  }                                                  

Thanks in advance to your support

You may use disabled property of the radiobuttonlist item for the same like below

 <RadzenRadioButtonList @bind-Value=@nullableValue TValue="int?" >
                                                <RadzenRadioButtonListItem Disabled=@(nullableValue==2) Text="A" Value="1" TValue="int?" />
                                                <RadzenRadioButtonListItem Disabled=@(nullableValue==1) Text="B" Value="2" TValue="int?" />

Hi, thanks to your reply.
So, when I wrote Disabled=@(nullableValue==2) all buttons are active it's not really what I want;
When I open DialogBox I want that all button is not active so nullableValue and when I choice one button the other (or all button) must be disabled;

Is it possible?

You can disable radiobutton list as below

<RadzenRadioButtonList Disabled==@(nullableValue==null) @bind-Value=@nullableValue TValue="int?" >

You need to use the above property as per your requirement. For further details do refer to the online demo