C# – WPF Bind checkbox to bool

ccheckboxmvvmwpfxaml

I have a WPF checkbox binded to ViewModel nullable boolean property. I am setting this property to false or true in Constructor, to avoid Interminent state but no matter what I do the Initial state of checkbox stays grayed. The binding working just fine since once I change the state by clicking the checkbox on UI I am getting controls values (true/false). Any Ideas?

XAML:

<CheckBox Margin="0,4,0,3"
          VerticalAlignment="Center"
          Content="Mutual"
          IsChecked="{Binding MutualChb}" />

ViewModel:

public ContstrutorViewModel()
{
    MutualChb = true;
}

private bool? _mutualChb;
public bool? MutualChb
{
    get { return _mutualChb; }
    set
    { 
        _mutualChb = value; 
        _mutualChb = ( _mutualChb != null ) ? value : false;
        OnPropertyChanged("MutualChb");
    }
}

Best Answer

The reason for that is because it's initially null.

private bool? _mutualChb;
public bool? MutualChb
{
    get { return (_mutualChb != null ) ? _mutualChb : false; }
    set
    { 
        _mutualChb = value;               
        OnPropertyChanged("MutualChb"); 
    }
}

Modern jQuery

Use .prop():

$('.myCheckbox').prop('checked', true);
$('.myCheckbox').prop('checked', false);

DOM API

If you're working with just one element, you can always just access the underlying HTMLInputElement and modify its .checked property:

$('.myCheckbox')[0].checked = true;
$('.myCheckbox')[0].checked = false;

The benefit to using the .prop() and .attr() methods instead of this is that they will operate on all matched elements.

jQuery 1.5.x and below

The .prop() method is not available, so you need to use .attr().

$('.myCheckbox').attr('checked', true);
$('.myCheckbox').attr('checked', false);

Note that this is the approach used by jQuery's unit tests prior to version 1.6 and is preferable to using $('.myCheckbox').removeAttr('checked'); since the latter will, if the box was initially checked, change the behaviour of a call to .reset() on any form that contains it – a subtle but probably unwelcome behaviour change.

For more context, some incomplete discussion of the changes to the handling of the checked attribute/property in the transition from 1.5.x to 1.6 can be found in the version 1.6 release notes and the Attributes vs. Properties section of the .prop() documentation.

Javascript – How to check whether a checkbox is checked in jQuery

How do I successfully query the checked property?

The checked property of a checkbox DOM element will give you the checked state of the element.

Given your existing code, you could therefore do this:

if(document.getElementById('isAgeSelected').checked) {
    $("#txtAge").show();
} else {
    $("#txtAge").hide();
}

However, there's a much prettier way to do this, using toggle:

$('#isAgeSelected').click(function() {
    $("#txtAge").toggle(this.checked);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="checkbox" id="isAgeSelected"/>
<div id="txtAge" style="display:none">Age is something</div>

Best Answer

Related Solutions

Javascript – Setting “checked” for a checkbox with jQuery

Modern jQuery

DOM API

jQuery 1.5.x and below

Javascript – How to check whether a checkbox is checked in jQuery

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