Dynamics 365 - Dynamically Add / Remove Values from a Multi-select Picklist

Following code can be used to dynamically remove a particular value from a multi-select option set:

function RemoveValuefromMultiSelectOptionSet(executionContext, valueInteger)

{

var formContext = executionContext.getFormContext();

formContext.ui.controls.getByName("new_multiselectpicklist1").removeOption(parseInt(valueInteger,10));

}

Similarly, in case a value needs to be added dynamically (or be brought back according to context), following code can be used: 

function AddValuefromMultiSelectOptionSet(executionContext, valueText, valueInteger)

{

var formContext = executionContext.getFormContext();

var newObj = { "text" : valueText, "value" : parseInt(valueInteger,10)};

formContext.ui.controls.getByName("new_picklist1").addOption(newObj);

}

Dynamics 365 - How to Get Selected Count of Multi-Select Picklist

Lets take an example of a multi-select picklist having 5 values: 

1. Banana
2. Orange
3. Strawberry
4. Guava 
5. Grapes

While working on the form, if a user selects only 2 out of these, e.g: 

1. Banana
2. Guava

Following JavaScript will return the count of selected values in the multi-select picklist i.e. 2. 

function GetMultiSelectPicklistLength(executionContext)

{

var length = 0;

var formContext = executionContext.getFormContext();

var multiSelectField = formContext.getAttribute("new_MultiselectPicklist");

if(multiSelectField != null)

{

var fieldValue = multiSelectField.getText();

if(fieldValue != null)

{

lengthValue = fieldValue.length;

}

}

return length;

}