MultiDataTrigger applies when all of the conditions are met not any, that's why your MultiDataTrigger isn't working.

Either have four separate triggers, or put the condition into a separate boolean property such as

bool ShowAssessment{    return Value == 301 || Value == 302 ...}

raise a property change notification for ShowAssessment when Value changes

e.g

int Value {     get{ return _value; }     set {         _value = value;         RaisePropertyChanged("Value");        RaisePropertyChanged("ShowAssessment");    }}

and then trigger on ShowAssessment.

Probably a better solution is to add a HeaderText property with a switch statement that returns the correct header text based on Value. Then just bind the header's text to that. No triggers required.

MultidataTrigger will act when all condition are satisfied . So

<MultiDataTrigger>    <MultiDataTrigger.Conditions>        <Condition Binding="{Binding Path=Prop1}" Value="301"/>        <Condition Binding="{Binding Path=Prop2}" Value="301"/>        <Condition Binding="{Binding Path=Prop3}" Value="302"/>        <Condition Binding="{Binding Path=Prop4}" Value="303"/>    </MultiDataTrigger.Conditions>    <Setter Property="Header" TargetName="expanderHeader" Value="Assessment"/></MultiDataTrigger>

You will require a single DataTrigger

<DataTrigger Binding="{Binding Path=ConditionEnum}" Value="1">    <Setter Property="Header" TargetName="expanderHeader" Value="Course Text"/></DataTrigger>

Set the Value of the Enum with a Defined logic in your code...

Example :

Validate(){    if(Value == 301 || Value == 302|| ....)    {        ConditionEnum = MyEnum.Assessment;    }    //Other Conditions}

I am leaving the implementation of INotifyPropertyChanged. Use it to provide change notifications.