I am trying to bind two boolean properties to two radio buttons. When the form loads, the two radio buttons are all unchecked. When I clicked the first radio button, it became checked. However, when I tried to click the second radio button, the first one stayed checked and the second one was still unchecked. If I clicked the second radio button again, both radio buttons are unchecked. If I clicked the second radio button again, it would become checked. Basically, it took 3 clicks to make the second radio button checked. Same applies to first radio button if I first checked the second radio button.

I have a viewmodel class:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace WinFormsApp1
{
    internal class ViewModel : INotifyPropertyChanged
    {
        private bool _isCashPayment;
        private bool _isChequePayment;

        public bool IsCashPayment
        {
            get => _isCashPayment;
            set
            {
                if (_isCashPayment == value)
                {
                    return;
                }
                _isCashPayment = value;


                // Notify the UI that the property has changed.
                OnPropertyChanged();
            }
        }

        public bool IsChequePayment
        {
            get => _isChequePayment;
            set
            {
                if (_isChequePayment == value)
                {
                    return;
                }

                _isChequePayment = value;

                // Notify the UI that the property has changed.
                OnPropertyChanged();
            }
        }

        public event PropertyChangedEventHandler? PropertyChanged;

        // Notify the UI that one of the properties has changed.
        private void OnPropertyChanged([CallerMemberName] string propertyName = "")
            => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

    }
}

The form code:

namespace WinFormsApp1
{
    public partial class Form7 : Form
    {
        private ViewModel _viewModel;

        public Form7()
        {
            InitializeComponent();
            _viewModel = new ViewModel();
        }

        private void Form7_Load(object sender, EventArgs e)
        {
            rdbCash.DataBindings.Add(nameof(rdbCash.Checked), _viewModel, nameof(_viewModel.IsCashPayment), false, DataSourceUpdateMode.OnPropertyChanged);
            rdbCheque.DataBindings.Add(nameof(rdbCheque.Checked), _viewModel, nameof(_viewModel.IsChequePayment), false, DataSourceUpdateMode.OnPropertyChanged);
        }
    }
}

Form designer generated code:

namespace WinFormsApp1
{
    partial class Form7
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            rdbCash = new RadioButton();
            rdbCheque = new RadioButton();
            button1 = new Button();
            SuspendLayout();
            // 
            // rdbCash
            // 
            rdbCash.AutoSize = true;
            rdbCash.Location = new Point(20, 66);
            rdbCash.Name = "rdbCash";
            rdbCash.Size = new Size(51, 19);
            rdbCash.TabIndex = 0;
            rdbCash.Text = "Cash";
            rdbCash.UseVisualStyleBackColor = true;
            // 
            // rdbCheque
            // 
            rdbCheque.AutoSize = true;
            rdbCheque.Location = new Point(136, 66);
            rdbCheque.Name = "rdbCheque";
            rdbCheque.Size = new Size(66, 19);
            rdbCheque.TabIndex = 1;
            rdbCheque.Text = "Cheque";
            rdbCheque.UseVisualStyleBackColor = true;
            // 
            // button1
            // 
            button1.Location = new Point(15, 28);
            button1.Name = "button1";
            button1.Size = new Size(75, 23);
            button1.TabIndex = 2;
            button1.Text = "button1";
            button1.UseVisualStyleBackColor = true;
            // 
            // Form7
            // 
            AutoScaleDimensions = new SizeF(7F, 15F);
            AutoScaleMode = AutoScaleMode.Font;
            ClientSize = new Size(800, 450);
            Controls.Add(button1);
            Controls.Add(rdbCheque);
            Controls.Add(rdbCash);
            Name = "Form7";
            Text = "Form7";
            Load += Form7_Load;
            ResumeLayout(false);
            PerformLayout();
        }

        #endregion

        private RadioButton rdbCash;
        private RadioButton rdbCheque;
        private Button button1;
    }
}

I am trying to use databinding instead of the traditional radio button checked event hander. I am expecting the radio button would change its state when clicked and also change the value of the binding property. I tried to put the two radio buttons in a group box and the result was the same.