Provides access to members that return information about the field.
Description
The field object represents a column in a table. A field has many properties, the most obvious ones being its name and its datatype. The esriFieldType enumeration lists the possible datatypes.
Members
| Name | Description | |
|---|---|---|
 |
AliasName | The alias name of the field. |
 |
CheckValue | Indicates if the value is valid given the field definition. |
|
DefaultValue | The default value of the field. |
|
Domain | The default domain of the field. |
|
DomainFixed | Indicates if the field's domain is fixed. |
|
Editable | Indicates if the field is editable. |
|
GeometryDef | The geometry definition for the field if IsGeometry is TRUE. |
|
IsNullable | Indicates if the field can contain null values. |
|
Length | The maximum length, in bytes, for values described by the field. |
|
Name | The name of the field. |
|
Precision | The precision for field values. |
|
RasterDef | The raster column definition. |
|
Required | Indicates if the field is required. |
|
Scale | The scale for field values. |
|
Type | The type of the field. |
|
VarType | The VARTYPE of the field (e.g. VT_I4). |
IField.AliasName Property
The alias name of the field.
Public ReadOnly Property AliasName As String
public string AliasName {get;}
Remarks
This is only supported on fields from object classes and feature classes that are registered with the geodatabase; Personal, File or ArcSDE geodatabases. For fields coming from other data sources (shapefiles, coverages, etc) the AliasName will be the same string as the field name.
IField.CheckValue Method
Indicates if the value is valid given the field definition.
Public Function CheckValue ( _
ByVal Value As Object _
) As Boolean
public bool CheckValue (
object Value
);
Description
CheckValue tests whether the specified value is valid for the current field, based upon the field type. For example, CheckValue will verify if the supplied value corresponds to field type of Small Integer or if the value corresponds to a string value.
The value is not checked against any existing domain.
IField.DefaultValue Property
The default value of the field.
Public ReadOnly Property DefaultValue As Object
public object DefaultValue {get;}
IField.Domain Property
The default domain of the field.
Public ReadOnly Property Domain As IDomain
public IDomain Domain {get;}
IField.DomainFixed Property
Indicates if the field's domain is fixed.
Public ReadOnly Property DomainFixed As Boolean
public bool DomainFixed {get;}
IField.Editable Property
Indicates if the field is editable.
Public ReadOnly Property Editable As Boolean
public bool Editable {get;}
Remarks
The Editable property of a field should always be set to TRUE. Setting it to FALSE will prevent all users from editing the contents of the field. To set a field to be read-only, use the IFieldInfo3.ReadOnly property.
It is best to loop through the fields of a feature and skip the fields that are not editable, rather than allowing users to attempt to edit fields that cannot be edited.
IField.GeometryDef Property
The geometry definition for the field if IsGeometry is TRUE.
Public ReadOnly Property GeometryDef As IGeometryDef
public IGeometryDef GeometryDef {get;}
IField.IsNullable Property
Indicates if the field can contain null values.
Public ReadOnly Property IsNullable As Boolean
public bool IsNullable {get;}
IField.Length Property
The maximum length, in bytes, for values described by the field.
Public ReadOnly Property Length As Integer
public int Length {get;}
IField.Name Property
The name of the field.
Public ReadOnly Property Name As String
public string Name {get;}
Remarks
Geodatabase feature classes, depending on their geometry type, may contain automatically generated fields for shape length and area. In personal and file geodatabases, these fields will be named using the name of the shape field suffixed with "_Length" and "_Area". In an SDE geodatabase, the names of these fields will be dependant on the underlying DBMS.
The IFeatureClass::ShapeFieldName property should be used to determine the name of the length and area fields for a feature class.
IField.Precision Property
The precision for field values.
Public ReadOnly Property Precision As Integer
public int Precision {get;}
Remarks
Precision is the number of digits in a number. For example, the number 56.78 has a precision of 4. Precision is only valid for fields that are numeric. Precision is always returned as 0 from personal or File geodatabase fields.
IField.RasterDef Property
The raster column definition.
Public ReadOnly Property RasterDef As IRasterDef
public IRasterDef RasterDef {get;}
IField.Required Property
Indicates if the field is required.
Public ReadOnly Property Required As Boolean
public bool Required {get;}
Description
All tables and feature classes have a set of required fields that are necessary to record the state of any particular object in the table or feature class. These required fields are automatically created when you create a new feature class or table, and cannot be deleted. Required fields may also have required properties such as its domain property. You cannot modify the required property of a required field.
For example, in a simple feature class, OID and Shape are required fields. They do have properties such as their alias and geometry type that you can modify, but these fields cannot be deleted.
The Required property only applies to changes to modifying the schema of a Field's properties or blocking it from being deleted. It has no impact on the ability to update or add\delete the values within the field. Also, setting the Required field property to be True will block the user from deleting the field through the GUI, as well as through ArcObjects.
IField.Scale Property
The scale for field values.
Public ReadOnly Property Scale As Integer
public int Scale {get;}
Remarks
Scale is the number of digits to the right of the decimal point in a number. For example, the number 56.78 has a scale of 2. Scale applies only to fields that are double. Scale is always returned as 0 from personal or File geodatabase fields.
IField.Type Property
The type of the field.
Public ReadOnly Property Type As esriFieldType
public esriFieldType Type {get;}
Remarks
For more information on the relation between esriFieldType values and the underlying SDE and DBMS data types, see the following articles in the ArcGIS Help:
- "A comparison of ArcGIS, ArcSDE, and DB2 data types"
- "A comparison of ArcGIS, ArcSDE, and Informix data types"
- "A comparison of ArcGIS, ArcSDE, and PostgreSQL data types"
- "A comparison of ArcGIS, ArcSDE, and Oracle data types"
- "A comparison of ArcGIS, ArcSDE, and SQL Server data types"
The following table outlines the equivalent field data types in ArcCatalog, ArcObjects and .NET:
| ArcCatalog | esriFieldType(IField::Type) | .NET Variable Type |
|---|---|---|
| Short Integer | esriFieldTypeSmallInteger | System.Int16 |
| Long Integer | esriFieldTypeInteger | System.Int32 |
| Float | esriFieldTypeSingle | System.Single |
| Double | esriFieldTypeDouble | System.Double |
| Text | esriFieldTypeString | System.String |
| Date | esriFieldTypeDate | System.DateTime |
| Object ID | esriFieldTypeOID | System.Int32 |
| Geometry | esriFieldTypeGeometry | ESRI.ArcGIS.Geometry.IGeometry |
| Blob | esriFieldTypeBlob | ESRI.ArcGIS.esriSystem.IMemoryBlobStream |
| Raster | esriFieldTypeRaster | ESRI.ArcGIS.Geodatabase.IRasterValue |
| GUID | esriFieldTypeGUID | System.String |
| GlobalID | esriFieldTypeGlobalID | System.String |
The following table outlines the Coverage, INFO Item to Geodatabase field mapping:
| Item type | Item width | Geodatabase field type (esriFieldType) |
|---|---|---|
| B | 4 | esriFieldTypeInteger |
| C | 1-320 | esriFieldTypeString |
| D | 8 | esriFieldTypeDate |
| F | 4 | esriFieldTypeSingle |
| F | 8 | esriFieldTypeDouble |
| I | 1-4 | esriFieldTypeSmallInteger |
| I | 5-9 | esriFieldTypeInteger |
| I | 10-16 | esriFieldTypeDouble |
| N | 1-9 | esriFieldTypeSingle |
| N | 10-16 | esriFieldTypeDouble |
The following table outlines the Shapefile, dBASE field to Geodatabase field mapping:
| Field type | Field width | Geodatabase field type (esriFieldType) |
|---|---|---|
| Date | - | esriFieldTypeDate |
| String | 1-255 | esriFieldTypeString |
| Boolean | - | esriFieldTypeString |
| Number | 1-16 (decimals = 0) | esriFieldTypeInteger |
| Number | 1-16 (decimals > 0) | esriFieldTypeDouble |
Note: Shapefiles only support date fields. Time is not supported. Geodatabases support date\time fields. If a shapefiles date field is queried for the time a default value of "12:00:00 AM" will be returned.
IField.VarType Property
The VARTYPE of the field (e.g. VT_I4).
Public ReadOnly Property VarType As Integer
public int VarType {get;}
Description
Returns an Integer indicating the subtype of a variable.
Remarks
The following is a list of the VARTYPE constants that can be returned from this property.
| Field type | VarType |
|---|---|
| esriFieldTypeSmallInteger**esriFieldTypeInteger**esriFieldTypeSingle**esriFieldTypeDouble**esriFieldTypeString**esriFieldTypeDate**esriFieldTypeOID**esriFieldTypeGeometry**esriFieldTypeBlob**esriFieldTypeRaster**esriFieldTypeGUID**esriFieldTypeGlobalID** | 234587313131388 |
Classes that implement IField
| Classes | Description |
|---|---|
| Field | Esri Field object. |
Remarks
When you create a field of type esriFieldTypeSingle, esriFieldTypeDouble or esriFieldTypeInteger, and specify zero for precision and scale, the geodatabase will attempt to create a binary type field if the underlying database supports it. Personal geodatabases support only binary type fields. ArcGIS ignores precision and scale of binary type fields.
The length property of a field has meaning only for esriFieldTypeString fields. The length property for all other field types is not important and will be ignored if specified.