Class Sql.ExpressionAttribute

An Attribute that allows custom Expressions to be defined for a Method used within a Linq Expression.

Inheritance

System.Object

MappingAttribute

Sql.ExpressionAttribute

Sql.ExtensionAttribute

Sql.FunctionAttribute

Sql.PropertyAttribute

Namespace: LinqToDB

Assembly: linq2db.dll

Syntax

public class ExpressionAttribute : MappingAttribute

Constructors

ExpressionAttribute(Nullable<String>)

Creates an Expression that will be used in SQL, in place of the method call decorated by this attribute.

Declaration

public ExpressionAttribute(string? expression)

Parameters

Type	Name	Description
System.Nullable<System.String>	expression	The SQL expression. Use {0},{1}... for parameters given to the method call.

ExpressionAttribute(String, Int32[])

Creates an Expression that will be used in SQL, in place of the method call decorated by this attribute.

Declaration

public ExpressionAttribute(string expression, params int[] argIndices)

Parameters

Type	Name	Description
System.String	expression	The SQL expression. Use {0},{1}... for parameters given to the method call.
System.Int32[]	argIndices	Used for setting the order of the method arguments being passed into the function.

ExpressionAttribute(String, String)

Creates an Expression that will be used in SQL, for the ProviderName specified, in place of the method call decorated by this attribute.

Declaration

public ExpressionAttribute(string configuration, string expression)

Parameters

Type	Name	Description
System.String	configuration	The Database configuration for which this Expression will be used.
System.String	expression	The SQL expression. Use {0},{1}... for parameters given to the method call.

ExpressionAttribute(String, String, Int32[])

Creates an Expression that will be used in SQL, for the ProviderName specified, in place of the method call decorated by this attribute.

Declaration

public ExpressionAttribute(string configuration, string expression, params int[] argIndices)

Parameters

Type	Name	Description
System.String	configuration	The Database configuration for which this Expression will be used.
System.String	expression	The SQL expression. Use {0},{1}... for parameters given to the method call.
System.Int32[]	argIndices	Used for setting the order of the method arguments being passed into the function.

Fields

UnknownExpression

Declaration

public static readonly SqlExpression UnknownExpression

Field Value

Type	Description
SqlExpression

Properties

ArgIndices

The order of Arguments to be passed into the function from the method call.

Declaration

public int[] ArgIndices { get; set; }

Property Value

Type	Description
System.Int32[]

CanBeNull

If true, result can be null

Declaration

public bool CanBeNull { get; set; }

Property Value

Type	Description
System.Boolean

Configuration

If null, this will be treated as the default evaluation for the expression. If set to a ProviderName, It will only be used for that provider configuration.

Declaration

public string? Configuration { get; set; }

Property Value

Type	Description
System.Nullable<System.String>

ExpectExpression

Used internally by Sql.ExtensionAttribute.

Declaration

public bool ExpectExpression { get; set; }

Property Value

Type	Description
System.Boolean

Expression

The expression to be used in building the SQL.

Declaration

public string? Expression { get; set; }

Property Value

Type	Description
System.Nullable<System.String>

IgnoreGenericParameters

if true, do not generate generic parameters.

Declaration

public bool IgnoreGenericParameters { get; set; }

Property Value

Type	Description
System.Boolean

InlineParameters

If true inline all parameters passed into the expression.

Declaration

public bool InlineParameters { get; set; }

Property Value

Type	Description
System.Boolean

IsAggregate

If true, this expression represents an aggregate result Examples would be SUM(),COUNT().

Declaration

public bool IsAggregate { get; set; }

Property Value

Type	Description
System.Boolean

IsNullable

Used to determine whether the return type should be treated as something that can be null If CanBeNull is not explicitly set.

Default is Undefined, which will be treated as true

Declaration

public Sql.IsNullableType IsNullable { get; set; }

Property Value

Type	Description
Sql.IsNullableType

IsPredicate

If true the expression is treated as a Predicate And when used in a Where clause will not have an added comparison to 'true' in the database.

Declaration

public bool IsPredicate { get; set; }

Property Value

Type	Description
System.Boolean

IsPure

If true, it notifies SQL Optimizer that expression returns same result if the same values/parameters are used. It gives optimizer additional information how to simplify query. For example ORDER BY PureFunction("Str") can be removed because PureFunction function uses constant value. For example Random function is NOT Pure function because it returns different result all time. But expression CurrentTimestamp is Pure in case of executed query. is also Pure function because it returns the same result with the same parameters.

Declaration

public bool IsPure { get; set; }

Property Value

Type	Description
System.Boolean

IsWindowFunction

If true, this expression represents a Window Function Examples would be SUM() OVER(), COUNT() OVER().

Declaration

public bool IsWindowFunction { get; set; }

Property Value

Type	Description
System.Boolean

Precedence

Determines the priority of the expression in evaluation. Refer to Precedence.

Declaration

public int Precedence { get; set; }

Property Value

Type	Description
System.Int32

PreferServerSide

If true a greater effort will be made to execute the expression on the DB server instead of in .NET.

Declaration

public bool PreferServerSide { get; set; }

Property Value

Type	Description
System.Boolean

ServerSideOnly

If true The expression will only be evaluated on the database server. If it cannot, an exception will be thrown.

Declaration

public bool ServerSideOnly { get; set; }

Property Value

Type	Description
System.Boolean

Methods

CalcCanBeNull(Sql.IsNullableType, IEnumerable<Boolean>)

Declaration

public static bool? CalcCanBeNull(Sql.IsNullableType isNullable, IEnumerable<bool> nullInfo)

Parameters

Type	Name	Description
Sql.IsNullableType	isNullable
IEnumerable<System.Boolean>	nullInfo

Returns

Type	Description
System.Nullable<System.Boolean>

GetCanBeNull(ISqlExpression[])

Declaration

protected bool GetCanBeNull(ISqlExpression[] parameters)

Parameters

Type	Name	Description
ISqlExpression[]	parameters

Returns

Type	Description
System.Boolean

GetExpression<TContext>(TContext, IDataContext, SelectQuery, Expression, Func<TContext, Expression, ColumnDescriptor, ISqlExpression>)

Declaration

public virtual ISqlExpression GetExpression<TContext>(TContext context, IDataContext dataContext, SelectQuery query, Expression expression, Func<TContext, Expression, ColumnDescriptor, ISqlExpression> converter)

Parameters

Type	Name	Description
TContext	context
IDataContext	dataContext
SelectQuery	query
Expression	expression
Func<TContext, Expression, ColumnDescriptor, ISqlExpression>	converter

Returns

Type	Description
ISqlExpression

Type Parameters

Name	Description
TContext

GetIsPredicate(Expression)

Declaration

public virtual bool GetIsPredicate(Expression expression)

Parameters

Type	Name	Description
Expression	expression

Returns

Type	Description
System.Boolean

GetObjectID()

Declaration

public override string GetObjectID()

Returns

Type	Description
System.String

Overrides

MappingAttribute.GetObjectID()

PrepareArguments<TContext>(TContext, String, Int32[], Boolean, List<Nullable<Expression>>, Nullable<List<SqlDataType>>, Func<TContext, Expression, ColumnDescriptor, ISqlExpression>)

Declaration

public static ISqlExpression[] PrepareArguments<TContext>(TContext context, string expressionStr, int[] argIndices, bool addDefault, List<Expression?> knownExpressions, List<SqlDataType>? genericTypes, Func<TContext, Expression, ColumnDescriptor, ISqlExpression> converter)

Parameters

Type	Name	Description
TContext	context
System.String	expressionStr
System.Int32[]	argIndices
System.Boolean	addDefault
List<System.Nullable<Expression>>	knownExpressions
System.Nullable<List<SqlDataType>>	genericTypes
Func<TContext, Expression, ColumnDescriptor, ISqlExpression>	converter

Returns

Type	Description
ISqlExpression[]

Type Parameters

Name	Description
TContext

PrepareParameterValues<TContext>(TContext, MappingSchema, Expression, ref Nullable<String>, Boolean, out List<Nullable<Expression>>, Boolean, out Nullable<List<SqlDataType>>, Func<TContext, Expression, ColumnDescriptor, ISqlExpression>)

Declaration

public static void PrepareParameterValues<TContext>(TContext context, MappingSchema mappingSchema, Expression expression, ref string? expressionStr, bool includeInstance, out List<Expression?> knownExpressions, bool ignoreGenericParameters, out List<SqlDataType>? genericTypes, Func<TContext, Expression, ColumnDescriptor, ISqlExpression> converter)

Parameters

Type	Name	Description
TContext	context
MappingSchema	mappingSchema
Expression	expression
System.Nullable<System.String>	expressionStr
System.Boolean	includeInstance
List<System.Nullable<Expression>>	knownExpressions
System.Boolean	ignoreGenericParameters
System.Nullable<List<SqlDataType>>	genericTypes
Func<TContext, Expression, ColumnDescriptor, ISqlExpression>	converter

Type Parameters

Name	Description
TContext

ResolveExpressionValues<TContext>(TContext, String, Func<TContext, String, Nullable<String>, Nullable<String>>)

Declaration

public static string ResolveExpressionValues<TContext>(TContext context, string expression, Func<TContext, string, string?, string?> valueProvider)

Parameters

Type	Name	Description
TContext	context
System.String	expression
Func<TContext, System.String, System.Nullable<System.String>, System.Nullable<System.String>>	valueProvider

Returns

Type	Description
System.String

Type Parameters

Name	Description
TContext

Extension Methods

Map.DeepCopy<T>(T)

Sql.IsDistinctFrom<T>(T, T)

Sql.IsNotDistinctFrom<T>(T, T)

SqlExtensions.In<T>(T, IEnumerable<T>)

SqlExtensions.In<T>(T, IQueryable<T>)

SqlExtensions.In<T>(T, T[])

SqlExtensions.In<T>(T, T, T)

SqlExtensions.In<T>(T, T, T, T)

SqlExtensions.NotIn<T>(T, IEnumerable<T>)

SqlExtensions.NotIn<T>(T, IQueryable<T>)

SqlExtensions.NotIn<T>(T, T[])

SqlExtensions.NotIn<T>(T, T, T)

SqlExtensions.NotIn<T>(T, T, T, T)