Apps - Legacy versus VB expressions

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Legacy Apps user guide

Getting Started
Demo apps
- Demos summary
How To
Notifications
Using VB Expressions
- Overview
- Limitations
- Using the Expression editor in controls
- The Query builder
  - Using the Fetch functions
- Migrating legacy apps to VB expressions
- Legacy versus VB expressions
- Useful VB functions
- Custom VB functions
Designing your App
Events and Rules
Leveraging RPA in your App
Leveraging Entities in Your App
Leveraging Queues in Your App
Leveraging Media in your app
- Referencing a media document in your app
- Binding a media document to Image controls
Leveraging Actions in your app
Leveraging Connections in your apps
Application Lifecycle Management (ALM)
- About ALM
UiPath First-Party Apps
- Automation Launchpad
Basic Troubleshooting Guide
- Apps Troubleshooting and FAQs

important :

For documentation on app projects in Studio Web, refer to the App Projects chapter in the Studio Web documentation: https://docs.uipath.com/studio-web/automation-cloud/latest/user-guide/apps-in-studio-web.

Legacy versus VB expressions

This section lists the common use cases for binding app elements, and how you can achieve the binding using legacy and VB expressions.

Using static string URLs in Image controls

Legacy	VB
Add the Image control. Set the URL/Value binding property to `https://path/to/the/image_file.jpg` Base64 images are also supported.	Add the Image control. Set the Source property to `new AppsFile("https://path/to/the/image_file.jpg")` Base64 images are also supported.

Using the File field of an entity in Image controls

Legacy	VB
In your app, reference the entity that holds the desired file. Bind the entity to a Table control. Add the Image control. Set the URL/Value binding property to the file.	In your app, reference the entity that holds the desired file. Bind the entity to a Table control. Add the Image control. Set the Source property to `MainPage.Table.SelectedItem.FileColumn`

Using files from a Storage Bucket in Image controls

Legacy	VB
In your app, reference the storage bucket that holds the desired file. Create an app variable of type AppsFile. For example `fileVar`. Add the Download file from Storage Bucket rule. Assign the downloaded file to the previously created app variable (`fileVar`). Add the Image control. Set the URL/Value binding property to `fileVar`.	In your app, reference the storage bucket that holds the desired file. Create an app variable of type AppsFile. For example `fileVar`. Add the Download file from Storage Bucket rule. Assign the downloaded file to the previously created app variable (`fileVar`). Add the Image control. Set the Source property to `fileVar`.

Using choice sets to populate List controls

Legacy	VB
Leverage entities in your app by using choice sets	In your app, reference the entity with the choice set. Add the List control. Set the List source property to `GetChoiceSet("entity_name")`. Set the Column property to the choice set name. Read this procedure for more information.

Referencing a choice set bound to List controls

Legacy	VB
Steps 4 and 5 in Leverage entities in your app by using choice sets	`<PAGE_NAME>.<CONTROL_NAME>.SelectedItem.<COLUMN_NAME>`<PAGE_NAME>.<CONTROL_NAME>.SelectedItem.<COLUMN_NAME>

Setting a single select choice set as the default value for controls

Dropdown, Radio Button and List controls support single select choice sets.

Legacy	VB
	`<PageName>.<ControlName>.DataSource.data.Select(Function(x) x.NumberId).ToList(0)`<PageName>.<ControlName>.DataSource.data.Select(Function(x) x.NumberId).ToList(0)

Setting a multiselect choice sets as the default value for controls

Multiselect Dropdown controls support multiselect choice sets.

Legacy VB

Legacy	VB
	`<PAGE_NAME>.<MULTISELECT_CONTROL_NAME>.DataSource.data.Where(Function(x) <VARIABLENAME>.<ENTITY_FIELD_OF_TYPE_CS>.contains(x.NumberId)).toList()`<PAGE_NAME>.<MULTISELECT_CONTROL_NAME>.DataSource.data.Where(Function(x) <VARIABLENAME>.<ENTITY_FIELD_OF_TYPE_CS>.contains(x.NumberId)).toList() To use this expression, ensure the entity variable is set to `selectedItem` using a Set Value rule.

<PAGE_NAME>.<MULTISELECT_CONTROL_NAME>.DataSource.data.Where(Function(x) <VARIABLENAME>.<ENTITY_FIELD_OF_TYPE_CS>.contains(x.NumberId)).toList()
<PAGE_NAME>.<MULTISELECT_CONTROL_NAME>.DataSource.data.Where(Function(x) <VARIABLENAME>.<ENTITY_FIELD_OF_TYPE_CS>.contains(x.NumberId)).toList()

To use this expression, ensure the entity variable is set to selectedItem using a Set Value rule.

Using static strings to populate List controls

Legacy	VB
`=["Value1", "Value2", "Value3"]`=["Value1", "Value2", "Value3"]	`AppsDataSource.from({"Value1", "Value2", "Value3"})`AppsDataSource.from({"Value1", "Value2", "Value3"})

Bind a date to Date Picker controls

Legacy	VB
To bind todays date, set the Default Date property to `=Now()`	To bind todays date, set the Default Date property to `DateOnly.FromDateTime(Now)`
To bind a specific date, for example 5th May 2021, set the Default Date property to `2021-01-05`	To bind a specific date, for example 5th May 2021, set the Default Date property to `new DateOnly(2021,1,25)`

Using an entity Date-Time field in Date Picker controls

Legacy	VB
Bind the required entity field to the Date Picker control.	`DateOnly.FromDateTime(customerEntityVar.DOB.Value.Date)`DateOnly.FromDateTime(customerEntityVar.DOB.Value.Date)

Computing the difference between two Date Picker values

Legacy	VB
N/A	`MainPage.Datepicker1.Value.Value.DayNumber - MainPage.Datepicker.Value.Value.DayNumber`MainPage.Datepicker1.Value.Value.DayNumber - MainPage.Datepicker.Value.Value.DayNumber

Referencing errors

You can reference the errors from the following rules:

Start Process
Entity rules
Queue rules
Trigger Workflow rule

Legacy	VB
Start Process rule: Handling Errors	In VB expressions, errors are exposed in the rule output. Reference an error as follows: `<PAGENAME>.<RULENAME>.Error.Message`<PAGENAME>.<RULENAME>.Error.Message `<PAGENAME>.<CONTROLNAME>.<RULENAME>.Error.Message`<PAGENAME>.<CONTROLNAME>.<RULENAME>.Error.Message

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NEXTUseful VB functions

Using static string URLs in Image controls​

Using the File field of an entity in Image controls​

Using files from a Storage Bucket in Image controls​

Using choice sets to populate List controls​

Referencing a choice set bound to List controls​

Setting a single select choice set as the default value for controls​

Setting a multiselect choice sets as the default value for controls​

Using static strings to populate List controls​

Bind a date to Date Picker controls​

Using an entity Date-Time field in Date Picker controls​

Computing the difference between two Date Picker values​

Referencing errors​