Variables in Apps

Use variables to store values between pages.

note

You can set a default value of the variable on page load by using the Set Value rule in the Loaded event of the page.

Apps supports creating variables of the following types:

AppsFile - file objects specific for Apps, which handles files uploading or downloading.
```
new AppsFile("https://imageURL.png")
```
Array - arrays of primitive data types or complex objects. For example:
- Array of strings : New String() {"Hello", "World"}
- Array of AppsFile: New AppsFile() { new AppsFile("Url1"), new AppsFile("Url2")}
- Array of entity type:
```
new Customer() { 
New Customer("1", "Baishali"), 
New Customer("2", "Viswa"), 
New Customer("3", "Evan") }
```
ChoiceSet - stores the choice set data of an entity. For example:
- GetChoiceSet("Team") - returns a ListSource with the choice set values.
- GetChoiceSetValue("Team", 1) - returns the indicated choice set value.

DataTable - a system data type used to store the value of a process Datatable output argument, or to create a custom Datatable, for example:

BuildDataTable(
    New DataTable("TestDT"), 
    New DataColumn(){ New DataColumn("Name"), New DataColumn("Age")},
    New List(Of Object) From { 
        AddDataRow(New Object(){"Baishali", "30"}), 
        AddDataRow(New Object(){"Viswa", "33"}) 
    },
    True
)

Date - for example, New System.DateTime (1993, 5, 31, 12, 35, 0).
DateOnly - a specific date, without time. For example, New System.DateOnly (2020, 04, 20).
DateTimeOffset - a date and time, relative to UTC. This structure includes a DateTime value and an Offset property, that defines the difference between the current DateTimeOffset date and the Coordinated Universal Time (UTC). For example:
```
new System.DateTimeOffset( new System.DateTime(2023, 5, 15, 7, 0, 0),
  new System.TimeSpan(-7, 0, 0) )
// output 5/15/2023 7:00:00 AM - 07:00
```
Decimal number - for example, 88.53.
Double
Guid - the unique identifier of an entity.
Int16
Int64
List<T> - for example:
- List of strings : New List(Of String) From {"string 1", "string 2", "string 3"}
- List of ListPair (for dropdown controls):
```
New List(Of Customer) From { 
New Customer("1", "Baishali"), 
New Customer("2", "Viswa"), 
New Customer("3", "Evan") }
```
ListSource - used to store the result of a entity query in a variable. You need to use the syntax ListSource(of <Entity_name>).
Nullable - used to define a null value. By default, all reference types, such as String, are nullable, but all value types, such as Int32, are not.
note
By default, primitive data types, except String, are non-nullable. Use this variable type to set them to null. For example, if you create an app variable of type Nullable, then you can set the value to "Nothing".
Object - stores any type.
Single - Used to store floating-point values that do not require the full data width of Double. The default value is 0.
Text (String) - for example, "Hello world"
True or false (Boolean)
UInt16 - holds unsigned 16-bit (2-byte) integers ranging in value from 0 through 65,535.
UInt32 - holds unsigned 32-bit (4-byte) integers ranging in value from 0 through 4,294,967,295.
UInt64 - holds unsigned 64-bit (8-byte) integers ranging in value from 0 through 18,446,744,073,709,551,615.
Whole number (Int32) - for example, 88