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DbExpression Class

Implements the basic functionality required by expression types.

Namespace:  System.Data.Common.CommandTrees
Assembly:  System.Data.Entity (in System.Data.Entity.dll)

public abstract class DbExpression

An expression is the fundamental building block of queries represented by a command tree. An expression represents some computation. Examples of expressions include constants, variables, functions, constructors, and standard relational operators like filter, join, and so on.

Every expression has a data type that designates the type of the result produced by that expression. The data type of the expression cannot be changed after creation.

An expression belongs to exactly one DbCommandTree. All sub-expressions of an expression must belong to the same DbCommandTree.

Expression trees are partially mutable: expression sub-trees can be replaced as long as the replacements have the same data type. The phrase expression sub-tree refers to the linkages between expressions.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5 SP1