Class PredicateBuilder

Helper functions for combining Linq expressions through logical operators

Inheritance

System.Object

PredicateBuilder

Inherited Members

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

System.Object.ToString()

Namespace: LemonEdge.Utils

Assembly: Utils.dll

Syntax

public static class PredicateBuilder

Methods

And<T>(Expression<Func<T, Boolean>>, Expression<Func<T, Boolean>>)

Combines the expr1 and expr2 logical expression into one expression that is true if both of the expressions are true

Declaration

public static Expression<Func<T, bool>> And<T>(Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)

Parameters

Type	Name	Description
System.Linq.Expressions.Expression<System.Func<T, System.Boolean>>	expr1	The first logical expression to be combined
System.Linq.Expressions.Expression<System.Func<T, System.Boolean>>	expr2	The second logical expression to be combined

Returns

Type	Description
System.Linq.Expressions.Expression<System.Func<T, System.Boolean>>	A new logical expression that returns true if expr1 and expr2 is true

Type Parameters

Name	Description
T	The type being evaluated in the expressions

Contains<TElement, TValue>(Expression<Func<TElement, TValue>>, IEnumerable<TValue>)

Creates an expression that returns true if the item has a value that is contained in the list of hardcoded values

Declaration

public static Expression<Func<TElement, bool>> Contains<TElement, TValue>(Expression<Func<TElement, TValue>> valueSelector, IEnumerable<TValue> values)

Parameters

Type	Name	Description
System.Linq.Expressions.Expression<System.Func<TElement, TValue>>	valueSelector	An expression of a function that given a TElement returns a TValue
System.Collections.Generic.IEnumerable<TValue>	values	A list of values to be compared against to see if an item has a value contained in this list

Returns

Type	Description
System.Linq.Expressions.Expression<System.Func<TElement, System.Boolean>>	An expression that returns true if an item contains a value within the values list

Type Parameters

Name	Description
TElement	The item type this expression is used against
TValue	The type of the value returned from an instance of the TElement that is used for comparrison against a list of items it may be contained in

Remarks

For example:

public class MyItem
{
    public int Value { get; set; }
    public string Label { get; set; }
    public override string ToString() => Label;
}

public static IEnumerable<MyItem> Test()
{
    var myList = new List<MyItem> { new MyItem { Value = 1, Label = "One" }, new MyItem { Value = 2, Label = "Two" }, new MyItem { Value = 3, Label = "Three" } };
    var where = PredicateBuilder.Contains((MyItem x) => x.Value, new int[] { 1, 2 });
    return myList.Where(where.Compile());
}

Would return:

One, Two

False<T>()

Declaration

public static Expression<Func<T, bool>> False<T>()

Returns

Type	Description
System.Linq.Expressions.Expression<System.Func<T, System.Boolean>>

Type Parameters

Name	Description
T

NotContains<TElement, TValue>(Expression<Func<TElement, TValue>>, IEnumerable<TValue>)

Creates an expression that returns true if the item has a value that is not contained in the list of hardcoded values

Declaration

public static Expression<Func<TElement, bool>> NotContains<TElement, TValue>(Expression<Func<TElement, TValue>> valueSelector, IEnumerable<TValue> values)

Parameters

Type	Name	Description
System.Linq.Expressions.Expression<System.Func<TElement, TValue>>	valueSelector	An expression of a function that given a TElement returns a TValue
System.Collections.Generic.IEnumerable<TValue>	values	A list of values to be compared against to see if an item has a value not contained in this list

Returns

Type	Description
System.Linq.Expressions.Expression<System.Func<TElement, System.Boolean>>	An expression that returns true if an item contains a value not found within the values list

Type Parameters

Name	Description
TElement	The item type this expression is used against
TValue	The type of the value returned from an instance of the TElement that is used for comparrison against a list of items it may not be contained in

Remarks

For example:

public class MyItem
{
    public int Value { get; set; }
    public string Label { get; set; }
    public override string ToString() => Label;
}

public static IEnumerable<MyItem> Test()
{
    var myList = new List<MyItem> { new MyItem { Value = 1, Label = "One" }, new MyItem { Value = 2, Label = "Two" }, new MyItem { Value = 3, Label = "Three" } };
    var where = PredicateBuilder.Contains((MyItem x) => x.Value, new int[] { 1, 2 });
    return myList.Where(where.Compile());
}

Would return:

Three

Or<T>(Expression<Func<T, Boolean>>, Expression<Func<T, Boolean>>)

Combines the expr1 and expr2 logical expression into one expression that is true if either of the expressions are true

Declaration

public static Expression<Func<T, bool>> Or<T>(Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)

Parameters

Type	Name	Description
System.Linq.Expressions.Expression<System.Func<T, System.Boolean>>	expr1	The first logical expression to be combined
System.Linq.Expressions.Expression<System.Func<T, System.Boolean>>	expr2	The second logical expression to be combined

Returns

Type	Description
System.Linq.Expressions.Expression<System.Func<T, System.Boolean>>	A new logical expression that returns true if either expr1 or expr2 is true

Type Parameters

Name	Description
T	The type being evaluated in the expressions

True<T>()

Declaration

public static Expression<Func<T, bool>> True<T>()

Returns

Type	Description
System.Linq.Expressions.Expression<System.Func<T, System.Boolean>>

Type Parameters

Name	Description
T