WhereExpression Class

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This is a Data Abstract for .NET Library topic

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Overview

The base abstract class for classes that represent WHERE expression tree nodes:

BinaryExpression combines two other expressions with a binary operator (such as equality or binary logical operators);
UnaryExpression represents expressions, based in the application of a unary operator (like the change of sign or logical negation) to another, inner expression;
BetweenExpression represents expression that checks belonging to a range of values;
ConstantExpression - the constant values that appear in an expression are represented through objects of this class;
ListExpression is a complex expression, represented by a list of expressions;
ParameterExpression - the parameters (variables) of an expression are represented through objects of this class;
FieldExpression represents the part of expression containing table field names;
NullExpression represents NULL values used in the expression;
MacroExpression represents a call to a macro function, which will be processed by Macro Processor.

This class is used to dynamically build WHERE statements from code (Dynamic Where feature of Data Abstarct).

For example, a WHERE part of this query

SELECT * FROM Employees WHERE ((Position = 'Sales Manager') 
OR (Zip IS NULL)) AND (City IN ('Atlanta GA', 'Seattle WA', 'New York CA'))

will be presented as:

WhereExpression lResult;
lResult = new BinaryExpression(new BinaryExpression(
            new BinaryExpression(
              new FieldExpression("Position"),
              new ConstantExpression("Sales Manager", DataType.String),BinaryOperator.Equal),
              new BinaryExpression(
              new FieldExpression("Zip"),
              new NullExpression(),BinaryOperator.Equal),BinaryOperator.Or),

              new BinaryExpression(
                new FieldExpression("City"),
                new ListExpression(
                new WhereExpression[]{ new ConstantExpression("Atlanta GA",DataType.String),
                                   new ConstantExpression("Seattle WA", DataType.String),
                                   new ConstantExpression("New York CA", DataType.String) }),
             BinaryOperator.In),

           BinaryOperator.And);

Location

Assembly: RemObjects.DataAbstract.dll
Namespace: RemObjects.DataAbstract.Expressions

Properties

Kind

Abstract readonly property, which represents the type of WHERE expression in the descendant class.

Prism: property Kind: WhereKind read
C#: WhereKind Kind { get; }
VB: Property ReadOnly Kind As WhereKind

Class Methods

Combine (WhereExpression, WhereExpression): WhereExpression
Creates new BinaryExpression from given aLeft and aRight operands, using operator And. Prism: `class method Combine(aLeft: WhereExpression; aRight: WhereExpression): WhereExpression` C#: `static WhereExpression Combine(WhereExpression aLeft, WhereExpression aRight)` VB: `Shared Function Combine(aLeft As WhereExpression, aRight As WhereExpression) As WhereExpression` Parameters: aLeft: aRight:
Combine (WhereExpression, WhereExpression, BinaryOperator): WhereExpression
Prism: `class method Combine(aLeft: WhereExpression; aRight: WhereExpression; anOperator: BinaryOperator): WhereExpression` C#: `static WhereExpression Combine(WhereExpression aLeft, WhereExpression aRight, BinaryOperator anOperator)` VB: `Shared Function Combine(aLeft As WhereExpression, aRight As WhereExpression, anOperator As BinaryOperator) As WhereExpression` Parameters: aLeft: aRight: anOperator:
FromString
Creates new WhereExpression from string, which should contain where node in the correct Dynamic Where XML Format. Prism: `class method FromString(aXml: String): WhereExpression` C#: `static WhereExpression FromString(String aXml)` VB: `Shared Function FromString(aXml As String) As WhereExpression` Parameters: aXml:
FromXmlNode
Creates new WhereExpression from xml node, which should be in the correct Dynamic Where XML Format. Prism: `class method FromXmlNode(aNode: XmlNode): WhereExpression` C#: `static WhereExpression FromXmlNode(XmlNode aNode)` VB: `Shared Function FromXmlNode(aNode As XmlNode) As WhereExpression` Parameters: aNode:
Validate
Validates that WhereExpression doesn't contain any errors, using WhereValidator. The main purpose of this validation - to scan all objects of WhereExpession tree and make sure that it contains correct field names. Validates that WhereExpression doesn't contain any errors, using WhereValidator. The main purpose of this validation - to scan all objects of WhereExpession tree and make sure that it contains correct field names. Prism: `class method Validate(anExpression: WhereExpression): Boolean` C#: `static Boolean Validate(WhereExpression anExpression)` VB: `Shared Function Validate(anExpression As WhereExpression) As Boolean` Parameters: anExpression:

Instance Methods

constructor
Prism: `constructor` C#: `constructor()` VB: `Sub New`
ApplyFieldMapping
Adjusts the field names in the WhereExpression in accordance with table names of fields in the given schema column mapping. Prism: `method ApplyFieldMapping(aColumnMappings: SchemaColumnMappingCollection)` C#: `void ApplyFieldMapping(SchemaColumnMappingCollection aColumnMappings)` VB: `Sub ApplyFieldMapping(aColumnMappings As SchemaColumnMappingCollection)` Parameters: aColumnMappings:
ApplyTableNameOrAlias
Prism: `method ApplyTableNameOrAlias(aName: String)` C#: `void ApplyTableNameOrAlias(String aName)` VB: `Sub ApplyTableNameOrAlias(aName As String)` Parameters: aName:
ExtractAllConstantExpression
Establishes a list of all ConstantExpression contained in the WhereExpression. Prism: `method ExtractAllConstantExpression(aExprList: List<ConstantExpression>)` C#: `void ExtractAllConstantExpression(List<ConstantExpression> aExprList)` VB: `Sub ExtractAllConstantExpression(aExprList As List<ConstantExpression>)` Parameters: aExprList:
ExtractAllFieldNames
Establishes a list of field names used in the WhereExpression. Prism: `method ExtractAllFieldNames(aFieldNames: List<String>)` C#: `void ExtractAllFieldNames(List<String> aFieldNames)` VB: `Sub ExtractAllFieldNames(aFieldNames As List<String>)` Parameters: aFieldNames:
ExtractAllParams
Fills SchemaParameterCollection with ParameterExpressions and ConstantExpressions (as ParameterExpressions) contained in the WhereExpression. Prism: `method ExtractAllParams(aParameters: SchemaParameterCollection)` C#: `void ExtractAllParams(SchemaParameterCollection aParameters)` VB: `Sub ExtractAllParams(aParameters As SchemaParameterCollection)` Parameters: aParameters:
ReadFromXml
Abstract method. In descendants creates WhereExpression from the given xml node, that should be in the correct Dynamic Where XML Format. Prism: `method ReadFromXml(xr: XmlNode)` C#: `void ReadFromXml(XmlNode xr)` VB: `Sub ReadFromXml(xr As XmlNode)` Parameters: xr:
ToSQLString ()
Prism: `method ToSQLString` C#: `String ToSQLString()` VB: `Function ToSQLString`
ToSQLString (StringBuilder)
Prism: `method ToSQLString(dest: StringBuilder)` C#: `void ToSQLString(StringBuilder dest)` VB: `Sub ToSQLString(dest As StringBuilder)` Parameters: dest:
ToXmlNode
Creates query node (in the Dynamic Where XML Format) from WhereExpression. Prism: `method ToXmlNode` C#: `XmlNode ToXmlNode()` VB: `Function ToXmlNode`
ToXmlString
Creates query node (in the Dynamic Where XML Format) from WhereExpression and returns it in the string format. Prism: `method ToXmlString` C#: `String ToXmlString()` VB: `Function ToXmlString`
Validate
Prism: `method Validate` C#: `Boolean Validate()` VB: `Function Validate`
WriteToXml
Abstract method. In descendants creates where node (in the Dynamic Where XML Format) from WhereExpression. Prism: `method WriteToXml(sw: XmlNode)` C#: `void WriteToXml(XmlNode sw)` VB: `Sub WriteToXml(sw As XmlNode)` Parameters: sw:

WhereExpression Class

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