To reproduce:
- Add two buttons and a textbox to a RadForm.
- Set the AcceptButton to be the first button.
- Focus the second button and press Enter

Workaround:
protected override bool ProcessCmdKey(ref System.Windows.Forms.Message msg, System.Windows.Forms.Keys keyData)
{
    if (keyData == System.Windows.Forms.Keys.Enter)
    {
        if (this.ActiveControl is Button && this.ActiveControl != this.AcceptButton)
        {
            ((Button)this.ActiveControl).PerformClick();
            return true;
        }
        
    }

    return base.ProcessCmdKey(ref msg, keyData);
}

To reproduce:
- Add a menu item with a specific mnemonic key to a form.
- Add child form with a button that has the same mnemonic key.
- Start the application hold Alt and press the mnemonic key.
- The menu item is executed instaed of the

My company is in the process of moving to windows 10 and we have a handful of custom systems that have to be migrated. I was told to "Just make them work". One of those is a tool that was written in 2008 using all Telerik controls. This system was last updated in 2012 to run on windows 7. We have plans to move the functionality to a Universal App however, we have bigger fish to fry. here is a list of all the bugs we encountered so far:

Forms with tons of controls(170 in my case) take forever to Initialize(> 60 seconds) especially the RadDateTimePicker;

The UI freezes until the InitializeComponent method  completes. 

The forms occasionally throws timeout errors waiting on a Com Handoff for more then 60 seconds.

There is no databinding going on and there is no functionality tied to the initialization or loading of the forms in an MDI. Only Large forms have this problem.

Any form that executes the following code does not load:
this.RootElement.ApplyShapeToControl = true;

To reproduce:

public Form1()
{
    InitializeComponent();
    this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle;
}

Although the user is not allowed to resize the form from the form's borders, it is possible to do it by the context menu.

Workaround:

[DllImport("user32.dll")]
static extern bool EnableMenuItem(IntPtr hMenu, uint uIDEnableItem, uint uEnable);

internal const UInt32 MF_DISABLED = 0x00000002;

internal const UInt32 SC_SIZE = 0xF000;

internal const UInt32 WM_INITMENUPOPUP = 0x0117;

protected override void WndProc(ref Message m)
{
    if (m.Msg == WM_INITMENUPOPUP && (((int)m.LParam & 0x10000) != 0))
    {
        EnableMenuItem(m.WParam, SC_SIZE, MF_DISABLED);
    }

    base.WndProc(ref m);
}

Please refer to the attached project.

Workaround: maximize the form in the Load event.

To reproduce:

private void radButton1_Click(object sender, EventArgs e)
{ 
    StringBuilder detailsText = new StringBuilder();
    for (int i = 0; i < 10; i++)
    {
        detailsText.AppendLine("Line" + i);
    }
    detailsText.AppendLine("END");

   RadMessageBox.Show("Message", "Caption Text", MessageBoxButtons.AbortRetryIgnore, detailsText.ToString());
}

Workaround: enlarge the details section in order to fit the text: 

 FieldInfo fi = typeof(RadMessageBoxForm).GetField("detailsSectionHeight", BindingFlags.NonPublic| BindingFlags.Instance);
fi.SetValue(RadMessageBox.Instance,200); 

Please refer to the attached sample project.

Workaround: call the Close method in the Shown event.

How to reproduce:
public partial class Form1 : Form
{
    Timer timer;

    public Form1()
    {
        InitializeComponent();

        timer = new Timer();
        timer.Interval = 1000; 
        timer.Tick += new EventHandler(MyTimer_Tick);
        timer.Start();
    }

    protected override void OnShown(EventArgs e)
    {
        base.OnShown(e);

        RadMessageBox.Show("Shown");
    }

    private void MyTimer_Tick(object sender, EventArgs e)
    {
        RadMessageBox.Show("Form closed");
        this.Close();
    }
}

Workaround: dispose the old instance
private void MyTimer_Tick(object sender, EventArgs e)
{
    RadMessageBox.Instance.Dispose();

    RadMessageBox.Show("Form closed");
    this.Close();
}

To reproduce: disable Aero on a Windows7 machine and use the following code:

public Form1()
{
    InitializeComponent();

    this.IsMdiContainer = true;

    Form MSform = new Form();
    MSform.Text = "Form MDI Child 1";
    MSform.MdiParent = this;
    MSform.Show();

    MSform = new Form();
    MSform.Text = "Form MDI Child 2";
    MSform.MdiParent = this;
    MSform.Show();
    
    MSform = new Form();
    MSform.Text = "Form MDI Child 3";
    MSform.MdiParent = this;
    MSform.Show();

    RadForm form = new RadForm();
    form.Text = "RadForm MDI Child 1";
    form.MdiParent = this;
    form.Show();

    form = new RadForm();
    form.Text = " RadFormMDI Child 2";
    form.MdiParent = this;
    form.Show();
    
    form = new RadForm();
    form.Text = " RadFormMDI Child 3";
    form.MdiParent = this;
    form.Show();
}

private void Form1_Shown(object sender, EventArgs e)
{
    this.LayoutMdi(MdiLayout.TileHorizontal);
}

private void radButton1_Click(object sender, EventArgs e)
{
    this.LayoutMdi(MdiLayout.TileVertical);
}

private void radButton2_Click(object sender, EventArgs e)
{
    this.LayoutMdi(MdiLayout.Cascade);
}

private void radButton3_Click(object sender, EventArgs e)
{
    this.LayoutMdi(MdiLayout.TileHorizontal);
}

Workaround: set the RadForm.AllowTheming property to false.

Workaround 2:  public class MyForm : RadForm
 {
     protected override CreateParams CreateParams
     {
         get
         {
             CreateParams par = base.CreateParams;
             par.Style |= NativeMethods.WS_CAPTION;
             return par;
         }
     }
 }

How to reproduce:
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        this.IsMdiContainer = true;
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        RadForm2 form = new RadForm2();
        form.Text = "MDI Child 1";
        form.MdiParent = this;
        form.ThemeName = "Desert";
        form.Show();
    }
}

public partial class RadForm2 : Telerik.WinControls.UI.RadForm
{
    public RadForm2()
    {
        InitializeComponent();

        this.AllowTheming = false;
    }
}

Workaround: override the ProcessCaptureChangeRequested method in the MDI child form
public partial class RadForm2 : Telerik.WinControls.UI.RadForm
{
    public RadForm2()
    {
        InitializeComponent();

        this.AllowTheming = false;
    }

    protected override bool ProcessCaptureChangeRequested(RadElement element, bool capture)
    {
        if (this.FormElement == null)
        {
            return this.Capture = capture;
        }

        return base.ProcessCaptureChangeRequested(element, capture);
    }
}

To reproduce: Please refer to the attached screenshots and sample project:

1. Disable Aero
2. Change to Windows Classic
3. Run the provided project

Workaround: change to Windows 7 aero Theme with disabled transparency.

Workaround: change all RadForms to inherit the following custom base form
public class RadFormBase : RadForm
{
    protected override void OnLoad(EventArgs e)
    {
        if (this.IsDesignMode)
        {
            this.BackColor = Color.Empty;
        }

        base.OnLoad(e);
    }

    public override Color BackColor
    {
        get
        {
            return this.ElementTree.RootElement.BackColor;
        }
        set
        {
            if (value == Color.Empty)
            {
                this.ElementTree.RootElement.ResetValue(VisualElement.BackColorProperty, ValueResetFlags.Local);
            }
            else
            {
                this.ElementTree.RootElement.BackColor = value;
            }
        }
    }
}