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Computed Fields

XRM supports a Computed field type that automatically calculates values from other fields or related records. Computed fields are read-only and evaluated on every read.

Field Types

Intra-record formulas (CR-020)

Reference other fields in the same record with arithmetic operators.

await fieldService.CreateAsync(entityId, new FieldDefinition
{
    Name = "TotalPrice",
    DisplayName = "Total Price",
    DataType = FieldDataType.Computed,
    Expression = "UnitPrice + ShippingCost"
});

Cross-record aggregates (CR-003)

Count or sum child records via relationships.

await fieldService.CreateAsync(entityId, new FieldDefinition
{
    Name = "OrderCount",
    DisplayName = "Number of Orders",
    DataType = FieldDataType.Computed,
    Expression = "COUNT(Order)"
});

await fieldService.CreateAsync(entityId, new FieldDefinition
{
    Name = "TotalRevenue",
    DisplayName = "Total Revenue",
    DataType = FieldDataType.Computed,
    Expression = "SUM(OrderLine.Amount)"
});

Expression Syntax

Operators

Operator Example
+ FieldA + FieldB
- Price - Discount
* Subtotal * 1.21
/ Total / Count
() (A + B) * C

Aggregate functions

Function Syntax Description
COUNT COUNT(EntityName) Count child records linked via relationship
SUM SUM(EntityName.FieldName) Sum a numeric field across child records

Rules

  • Field names are case-sensitive and must match exactly
  • Numeric literals use dot decimal: 1.21, 100, 0.5
  • Missing or null fields resolve to 0
  • Division by zero returns 0
  • Invalid expressions return no value (field stays empty)

Behavior

  • Evaluated on read — never stored in the database
  • Always current — reflects latest data from record and children
  • Skipped in validation — cannot be set by user or API
  • Displayed read-only — rendered with locale formatting (Decimal format)
  • Available in lists — computed values appear in record grids
  • Available via API — GET responses include computed values

Aggregates and Relationships

COUNT(EntityName) and SUM(EntityName.FieldName) work via XRM's relationship system:

  • The computed field must be on the parent entity
  • The EntityName in the expression must match the child entity's Name
  • A relationship must exist linking parent → child
  • Only records linked via RecordLink are counted/summed

Examples

Tax calculation

Expression = "Subtotal * 0.21"

Gross from net + tax

Expression = "Subtotal + Tax"

(Where Tax is itself a computed field — computed fields can reference other computed fields)

Count related records

Expression = "COUNT(Contact)"

Sum a child field

Expression = "SUM(OrderLine.Amount)"

Combined: arithmetic + aggregate

Expression = "SUM(OrderLine.UnitPrice) + SUM(OrderLine.Shipping)"

Via the API

POST /api/entities/{entityId}/fields
Content-Type: application/json

{
  "name": "TotalPrice",
  "dataType": "Computed",
  "expression": "UnitPrice + ShippingCost"
}

The computed value appears in GET responses but is ignored in POST/PUT payloads.