Uncheck checkbox when another is checked - wpf

Question

I have two checkboxes. When I check one, I want the other to uncheck if it's currently checked. Both can be unchecked. Currently, I can check one, but when I check the other, both of them uncheck. I'm having trouble figuring out why.
Note: I want to do this all in the .xaml if possible. I've been messing with data triggers to get the proper effect with no luck so far.
<CheckBox Name="SYOChkBox">
<CheckBox.Style>
<Style TargetType="CheckBox">
<Style.Triggers>
<DataTrigger Binding="{Binding IsChecked, ElementName=UTMChkBox}"
Value="True">
<Setter Property="IsChecked"
Value="False" />
</DataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
</CheckBox>
<CheckBox Name="UTMChkBox">
<CheckBox.Style>
<Style TargetType="CheckBox">
<Style.Triggers>
<DataTrigger Binding="{Binding IsChecked, ElementName=SYOChkBox}"
Value="True">
<Setter Property="IsChecked"
Value="False" />
</DataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
</CheckBox>

Answer 1

You should really be using a ViewModel to do this (I'll leave a snippet on how you could do it using a VM at the end of the post).
Anyway, here's what I was able to do with XAML only
Using CheckBox
The problem with using this approach is that when both are checked, both of the triggers will be triggered (??), and both will be unchecked. So, I guess what you can do is this:
CheckBox X will normally uncheck when you check CheckBox Y, but CheckBox X just won't check while CheckBox Y is checked.
<CheckBox Name="SYOChkBox">
<CheckBox.Style>
<Style TargetType="CheckBox">
<Style.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding IsChecked, ElementName=UTMChkBox}" Value="True" />
<Condition Binding="{Binding IsChecked, ElementName=SYOChkBox}" Value="True" />
</MultiDataTrigger.Conditions>
<Setter Property="IsChecked" Value="False" />
</MultiDataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
</CheckBox>
<CheckBox Name="UTMChkBox" />
Using RadioButton
I know it isn't what you asked, but as a sugestion, you could use a RadioButton, the code would be a lot cleaner:
<RadioButton>Option A</RadioButton>
<RadioButton>Option B</RadioButton>
<RadioButton>None</RadioButton>
Using ViewModel
XAML
<CheckBox IsChecked="{Binding IsChecked_CheckBoxA}" />
<CheckBox IsChecked="{Binding IsChecked_CheckBoxB}" />
Code-behind:
private bool _IsChecked_CheckBoxA;
private bool _IsChecked_CheckBoxB;
public bool IsChecked_CheckBoxA
{
get
{
return _IsChecked_CheckBoxA;
}
set
{
if (value)
IsChecked_CheckBoxB = false;
_IsChecked_CheckBoxA = value;
NotifyPropertyChanged();
}
}
public bool IsChecked_CheckBoxB
{
get
{
return _IsChecked_CheckBoxB;
}
set
{
if (value)
IsChecked_CheckBoxA = false;
_IsChecked_CheckBoxB = value;
NotifyPropertyChanged();
}
}

Answer 2

As others have said, it might not be doable in just xaml, and using a viewmodel is suggested. So here's what I have that works:
Xaml:
<CheckBox Name="SYOChkBox"
IsChecked="{Binding IsCheckedSYO}" />
<CheckBox Name="UTMChkBox"
IsChecked="{Binding IsCheckedUTM}" />
Viewmodel:
private bool _isCheckedSYO;
public bool IsCheckedSYO
{
get { return _isCheckedSYO; }
set
{
if (true == value) //if checked
{
IsCheckedUTM = false; //uncheck the UTM check box
_isCheckedSYO = value;
}
else
{
_isCheckedSYO = value;
}
OnPropertyChanged("IsCheckedSYO");
}
}
private bool _isCheckedUTM;
public bool IsCheckedUTM
{
get { return _isCheckedUTM; }
set
{
if (true == value) //if checked
{
IsCheckedSYO = false; //uncheck the SYO checkbox
_isCheckedUTM = value;
}
else
{
_isCheckedUTM = value;
}
OnPropertyChanged("IsCheckedUTM");
}
}