Check one Radio button by Default .NET MAUI

Here a simple calculator to perm Add/Sub/Div /Multiply between Whole number and Fractions.

I got help from this form to load the radio button group

{ Addition, Substraction ,Multiplication,Division}

But I want one Radio Button to be checked by default say add, please suggest.

namespace MauiAppMCQs.Models
{
    public class FractionEnums
    {
        public enum Calulation { Addition, Substraction ,Multiplication,Division}
    }
}
@page "/WholeFracCalc"
@using System.ComponentModel.DataAnnotations;
@using MauiAppMCQs.Models;
@using static MauiAppMCQs.Models.FractionEnums;
<h3>Whole Number (Divide/Multiply/Add/Substract )Fractions Calculator</h3>
 
 
<PageTitle>Calculator</PageTitle>
 
<div >
   
    <fieldset>
        <legend>Whole Number   </legend>
        <InputNumber @bind-Value="num1" disabled=@isdisabled />
        
     
    </fieldset>
         <fieldset disabled=@isdisabled>
        
        <InputRadioGroup @bind-Value="Calulation" >
            @foreach (var calculationItem in Enum.GetValues<Calulation>())
            {
                <div>
                    <label>
                        <InputRadio Value="calculationItem" />
                        @calculationItem
                    </label>
                </div>
            }
        </InputRadioGroup>
    </fieldset>
        <br />
   
    <br /> 
<div class="col-md-4">
        <table border="1" disabled=@isdisabled>
            <tr>
                <th colspan="2"> Fraction</th>
               
            </tr>
            <tr>
                 
                <td>
                    <input placeholder="Enter Numerator" disabled=@isdisabled @bind="@num2"> <br>
                    <input placeholder="Enter Denominator" disabled=@isdisabled @bind="@den2">
                </td>
            </tr>
        </table>
    </div>
        
    
    
    
    <legend>Step1 </legend>
        <br />
        <div>@operation</div>
        <br />
        
        <div>@tempresult</div>
        <br />
        <legend>Step2(HCF) </legend>
        <br />
        <div>@hcf</div>
        <br />
        <legend>Result</legend>
        <div>@result</div>
        <br />
        <div>@decresult</div>
    
    <br>
    <div>
        <button @onclick="Calculate">Calculate</button>
    </div>
    <div>
        @errmsg
    </div>
    <br>
    <button @onclick="Clear" >
        Clear
    </button>
    <br />
    @errmsg
</div>
@code {
    [Required, EnumDataType(typeof(Calulation))]
    public Calulation? Calulation { get; set; } = null; public string skip; public string type;
    private bool isdisabled = false; public string errmsg = "";
    public class FractionEnums
    {
        public enum Calulation { Addition, Substraction, Multiplication, Division }
    }
    public int num1; public int num2; public int den1=1; public int den2=0; public int resnum; public int resden;
    public int tempnum; public int tempden; public string result; public string tempresult;int hcf ; public string checkops; public string operation; public double decresult;
    private void Calculate()
    {
        den1 = 1;
        if ((num1 > -50) || (num1 <= -50))
        {
            isdisabled = true;
        }
        errmsg = "";
        skip = "N"; checkops = "N";
        if ((num1 <= -50))
        { skip = "Y"; isdisabled = false; }
        if ((num2 <= -50))
        { skip = "Y"; isdisabled = false; }
        if ((num1 > 50))
        { skip = "Y"; isdisabled = false; }
        if ((num2 > 50))
        { skip = "Y"; isdisabled = false; }
       
        if ((den2 > 50) || (den2 <= 1))
        { skip = "Y"; isdisabled = false; }
        if (skip == "N")
        {
            if (Calulation == MauiAppMCQs.Models.FractionEnums.Calulation.Addition)
            {
                checkops = "Y"; tempnum = num1 * den2 + num2 * den1; operation = "Addition   (numerator1 × denominator2 + numerator2 × 1)/( 1 × denominator2 )";
                tempden = den1 * den2;
                int i;
                int hcfin;int hcfout;
                hcfin = tempnum;
                hcfout = tempden;
                if(hcfin<0)
                { hcfin = hcfin * -1; }
                hcf=calchcf(hcfin, hcfout);
                tempresult = tempnum.ToString() + @"/" + tempden.ToString();
                resnum = tempnum / hcf; 
                resden = tempden / hcf;
                result = resnum.ToString() + @"/" + resden.ToString();
                if(resden==1)
                { result = resnum.ToString(); }
                double tempdec = (Convert.ToDouble(resnum) / Convert.ToDouble(resden));
                decresult = Math.Round(tempdec, 2);
            }
            if (Calulation == MauiAppMCQs.Models.FractionEnums.Calulation.Substraction)
            {
                checkops = "Y";
                tempnum = num1 * den2 - num2 * den1; operation = "Substraction (numerator1 × denominator2 - numerator2 x  1)/( 1 × denominator2 )";
                tempden = den1 * den2;
                int hcfin;
                int hcfout;
                hcfin = tempnum;
                hcfout = tempden;
                if (hcfin < 0)
                { hcfin = hcfin * -1; }
                int i;
                hcf = calchcf(hcfin, hcfout);
                resnum = tempnum / hcf;
                resden = tempden / hcf;
                tempresult = tempnum.ToString() + @"/" + tempden.ToString();
                result = resnum.ToString() + @"/" + resden.ToString();
                if (resden == 1)
                { result = resnum.ToString(); }
                double tempdec = (Convert.ToDouble(resnum) / Convert.ToDouble(resden));
                decresult = Math.Round(tempdec, 2);
            }
            if (Calulation == MauiAppMCQs.Models.FractionEnums.Calulation.Multiplication)
            {
                checkops = "Y";
                tempnum = num1 * num2; operation = "Multiplication ((numerator1 × numerator 2)/(1 × denominator2 ))";
                tempden = den1 * den2;
                int hcfin;
                int hcfout;
                hcfin = tempnum;
                hcfout = tempden;
                if (hcfin < 0)
                { hcfin = hcfin * -1; }
                int i;
                hcf = calchcf(hcfin, hcfout);
                resnum = tempnum / hcf;
                resden = tempden / hcf;
                tempresult = tempnum.ToString() + @"/" + tempden.ToString();
                result = resnum.ToString() + @"/" + resden.ToString();
                if (resden == 1)
                { result = resnum.ToString(); }
                double tempdec = (Convert.ToDouble(resnum) / Convert.ToDouble(resden));
                decresult = Math.Round(tempdec, 2);
            }
            if (Calulation == MauiAppMCQs.Models.FractionEnums.Calulation.Division)
            {
                checkops = "Y";
                tempnum = num1 * den2; operation = "Division ((numerator1 × denominator2)/( 1 × numerator 2 ))";
                tempden = den1 * num2;
                int hcfin;
                int hcfout;
                hcfin = tempnum;
                hcfout = tempden;
                if (hcfin < 0)
                { hcfin = hcfin * -1; }
                int i;
                hcf = calchcf(hcfin, hcfout);
                resnum = tempnum / hcf;
                resden = tempden / hcf;
                tempresult = tempnum.ToString() + @"/" + tempden.ToString();
                result = resnum.ToString() + @"/" + resden.ToString();
                if (resden == 1)
                { result = resnum.ToString(); }
                double tempdec = (Convert.ToDouble(resnum) / Convert.ToDouble(resden));
                decresult = Math.Round(tempdec, 2);
            }
        }
        else
        { errmsg = "Enter Whole Number or Numerator  between -50 and  50 and Denominator between 1 to 50 "; checkops = "Y"; }
        if(checkops == "N")
        { errmsg = "Check a Radio Button "; }
    } 
    private  int calchcf(int a, int b)
    { int i;
        int hcfin = a; int hcfout = b; int hcfres = 1;
        for (i = 1; i <= hcfin || i <= hcfout; ++i)
        {
            if (hcfin % i == 0 && hcfout % i == 0)
            {
                hcfres = i;
            }
        }
        return hcfres;
    }
    private void Clear()
    {
        num1 = 0; num2=0; den1 = 0;den2 = 0; isdisabled = false; resnum = 0; resden = 0;result = "";decresult = 0;
        tempnum = 0; tempden = 0;operation = "";
    }
}