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field-types.md

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Field Types

All database columns are represented by a TField subclass. Every TField starts as null and tracks null state independently of the CLR value.

Common API (all TField subtypes)

field.IsNull()            // true if no value has been set
field.IsLoaded()          // true if loaded from DB (set by ORM after a Read/Query)
field.SetValue(object v)  // set a value (clears null)
field.SetNull(bool isNull)// force null state
field.SetLoaded(bool b)   // mark as loaded (used internally)
field.GetValue()          // returns boxed CLR value
field.GetRawValue()       // returns raw object (may differ from GetValue for mapped types)
field.CopyFrom(TField src)// copy value + null state from another field
field.IsValid()           // false if SetValidationFailure(true) was called
field.ConversionErrorOccurred() // true if SetValue received an unconvertible value

Numeric Types

Type CLR Type Notes
TInt int 32-bit signed integer; ++/-- operators
TInt16 short 16-bit integer
TInt64 / TLong long 64-bit integer
TByte byte 8-bit unsigned
TSByte sbyte 8-bit signed
TUInt uint 32-bit unsigned
TUInt16 ushort 16-bit unsigned
TUInt64 ulong 64-bit unsigned
TFloat float Single precision
TDouble double Double precision
TDecimal decimal Monetary / high-precision; comparison operators

All numeric types support:

  • Implicit conversion to/from their CLR type
  • ==, !=, >, <, >=, <= operators
  • GetHashCode() returning 0 when null

String Types

Type CLR Type Notes
TString string Empty string ≠ null; Length, Contains, ToUpper, ToLower, Trim, Clone
TChar char Single character
THtmlString string Like TString; HTML-aware subclass
TIpAddress string IP address stored as string

TString does not convert empty string to null. Use SetNull(true) explicitly.

var s = new TString("hello");
string raw = s;         // implicit → "hello"
TString ts = "world";  // implicit ← "world"
bool eq = s == "hello"; // mixed equality

Key Types

Type CLR Type Notes
TPrimaryKey int Auto-generated PK; implicit from int / long; converts to TForeignKey
TForeignKey int References another table's PK; implicit from int / long 
TPrimaryKey pk = 42;        // implicit from int
TForeignKey fk = pk;        // TPrimaryKey → TForeignKey (creates new instance)
bool equal = pk == (TForeignKey)pk; // safe cross-type comparison via explicit cast

Note: The operators pk == fk and pk != fk may throw at runtime due to an unsafe internal cast. Always convert explicitly: (TForeignKey)pk == fk.

Date/Time Types

Type CLR Type Notes
TDateTime DateTime Local or unspecified datetime
TUtcDateTime DateTime Always UTC
TLocalDateTime DateTime Always local time
TDate DateTime Date only (time truncated)
TUtcDate DateTime UTC date only
TLocalDate DateTime Local date only
TTime TimeSpan Time of day

Boolean

Type CLR Type Notes
TBool bool Stores true/false; implicit from bool

Binary / GUID

Type CLR Type Notes
TByteArray byte[] Binary data
TGuid Guid UUID / uniqueidentifier

Factory

Create a TField instance dynamically:

// By type
TField f = TField.Create(typeof(TString), null);

// By fully-qualified name
TField g = TField.Create("ActiveForge.TDecimal");

All factory-created instances start as null (IsNull() == true).