2023-11-05 - In IL: Field Definitions
In IL
- Part 1 - Introduction
- Part 2 - Variables and Types
- Part 3 - Variables in Visual Basic .NET
- Part 4 - Instructions and the Stack
- Part 5 - Volume of a Cylinder (Operations)
- Part 6 - Branching Instructions
- Part 7 - Largest of Two Numbers (if-else)
- Part 8 - Largest of Three Numbers (If-ElseIf-Else)
- Part 9 - Switch instruction
- Part 10 - Grade Analyser (switch)
- Part 11 - Prize Calculator (switch-2)
- Part 12 - VB Grade Analyser (Select)
- Part 13 - Loop Instructions
- Part 14 - Print the Alphabet (while)
- Part 15 - Print the Alphabet (do while, for)
- Part 16 - Print the Alphabet (Do Until)
- Part 17 - Print the Alphabet (break, continue)
- Part 18 - Array Instructions
- Part 19 - Summing Arrays
- Part 20 - Other Instructions
- Part 21 - Assemblies
- Part 22 - Class Definitions
- Part 23 - C# Classes and Structs
- Part 24 - VB Classes, Modules and Structures
- Part 25 - Field Definitions
- Part 26 - Field Declarations
Fields are used to store information as part of a type.
.field <attributes…> <type> <Id> <initializer>
A field is declared using the .field directive. This is followed by a set of attributes which describe how the field behaves. The type indicates what kind of data the field contains, Id is the name of the field, and the initializer is used to set the value of the field
There are a variety of attributes that can be set.
Accessibility
The accessibility attributes are used to indicate where the field can be accessed.
| Attribute | Description |
|---|---|
| private | Visible only within the containing class |
| famandassem | Visible to containing class and derived classes within the same assembly |
| assembly | Visible to the containing assembly |
| family | Visibility to containing class and derived classes |
| famorassem | Visibility to containing class and derived classes or to the containing assembly |
| public | Visible everywhere |
Contract Attributes
The contract attributes are used to control how the field can be used
| Attribute | Description |
|---|---|
| static | Indicates that the field is associated with the type. Not specifying static means that the field is specific to each instance |
| initonly | Indicates that the field can only be modified in a constructor |
| literal | (static only) indicates that the field can only have the value specified as part of its declaration |
Interoperation Attributes
The marshal (<NativeType>) attribute is used to specify how this field should be handled during marshalling
Special attributes
These attributes are used to indicate that the field should be treated in a special way
| Attribute | Description |
|---|---|
| rtspecialname | The field has a special meaning to the runtime |
| specialname | The field has a special meaning to something besides the runtime |
Type
We saw examples of types when we looked at variables. User defined value types start with valuetype and reference types start with class. This is followed by the fully qualified name of the type including namespaces and the source assembly. Built-in types use the simple name of the type and value or reference type is implied.
Initialization
initialization is specified using an equal sign followed by <type>(<value>) where type is one of the built-in types and value is the value to initialize the variable with.
Next time we will look at some examples.
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