# C1.CalcEngine.ExpressionEngine.IExpressionSyntax ## Content

IExpressionSyntax Interface

Defines the properties and methods of a class that contains the syntax of an expression engine.

public interface IExpressionSyntax

Public Interface IExpressionSyntax

Name	Description
IdentifierChars	Gets or sets a string that specifies special characters that are valid for identifiers.
StringQuotes	Gets a collection of opening and closing quotes for strings.

Name	Description
AddItem(ExpressionItem)	Adds an ExpressionItem to the items collection.
ClearItems()	Clear all items from the error collection.
GetFieldName(string)	Gets the field name from the data source.
RegisterConstant(string, object)	Registers a constant that can be evaluated by expression engine.
RegisterFields()	Registers the data source field names that can be evaluated by expression engine.
RegisterFunction(string, int, Func<List<IExpression>, object>, ItemType)	Registers a function that can be evaluated by expression engine.
RegisterFunction(string, int, int, Func<List<IExpression>, object>, ItemType)	Registers a function that can be evaluated by expression engine.
RegisterToken(object, TKID, TKTYPE)	Registers a token that can be evaluated by expression engine.
RegisterVariable(string, object)	Registers a variable that can be evaluated by expression engine.