Class ExpressionsHelper

A set of helper functions and extensions around expressions and reflection for Linq functionality

Inheritance

object

ExpressionsHelper

Inherited Members

object.GetType()

object.MemberwiseClone()

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

Namespace: LemonEdge.Utils

Assembly: LemonEdge.Utils.dll

Syntax

public static class ExpressionsHelper

Methods

ChangeTo<T, TT>(Expression<Func<T, bool>>)

Converts an expression from one type to another

Declaration

public static Expression<Func<TT, bool>> ChangeTo<T, TT>(this Expression<Func<T, bool>> expr) where TT : T

Parameters

Type	Name	Description
Expression<Func<T, bool>>	expr	The expression to convert to type TT

Returns

Type	Description
Expression<Func<TT, bool>>	The old expression converted to type TT

Type Parameters

Name	Description
T	The original type of an expression
TT	The new type of the expression

Remarks

For example:

public interface IMyItem
{
    int Value { get; set; }
}
public class MyItem : IMyItem
{
public int Value { get; set; }
public override string ToString() => Value.ToString();
}
public class Example
{
public IEnumerable<MyItem> ChangeType()
{
Expression<Func<IMyItem, bool>> expr = x => x.Value > 10;
var newExpress = expr.ChangeTo<IMyItem, bool>();
var items = new List<MyItem>() { new MyItem() { Value = 5 }, new MyItem() { Value = 15 } };
return items.Where(newExpress.Compile());
}
}

Would return: 15

GetPropertyInfo<TSource, TProperty>(Expression<Func<TSource, TProperty>>)

Returns the PropertyInfo definition for the specified property against this type TSource

Declaration

public static PropertyInfo GetPropertyInfo<TSource, TProperty>(this Expression<Func<TSource, TProperty>> propertyLambda)

Parameters

Type	Name	Description
Expression<Func<TSource, TProperty>>	propertyLambda	An expression returning the property to retrieve the PropertyInfo of

Returns

Type	Description
PropertyInfo	The PropertyInfo definition for the specified property against this type TSource

Type Parameters

Name	Description
TSource	The type of item this expression is against
TProperty	The type of the property returned from the expression

Remarks

For example:

public class MyItem
{
    public int Value { get; set; }
}

public static PropertyInfo GetPropInfo()
{
    Expression<Func<MyItem, int>> expr = x => x.Value;
    return expr.GetPropertyInfo();
}

GetPropertyValue<T>(Expression<Func<T>>)

Compiles an expression and gets the functions return value

Declaration

public static T GetPropertyValue<T>(this Expression<Func<T>> lambda)

Parameters

Type	Name	Description
Expression<Func<T>>	lambda	The expression to compile

Returns

Type	Description
T

Type Parameters

Name	Description
T	The type of return value

GetPropertyValue<In, T>(Expression<Func<In, T>>, In)

Compiles an expression and gets the functions return value

Declaration

public static T GetPropertyValue<In, T>(this Expression<Func<In, T>> lambda, In input)

Parameters

Type	Name	Description
Expression<Func<In, T>>	lambda	The expression to compile
In	input

Returns

Type	Description
T

Type Parameters

Name	Description
In	The input to the expression
T	The type of return value

OrderByDescendingPropNameGeneric(IQueryable, Type, string)

Orders the specified query by the specified property name in descending order

Declaration

public static IQueryable OrderByDescendingPropNameGeneric(this IQueryable q, Type type, string propName)

Parameters

Type	Name	Description
IQueryable	q	The query
Type	type	The type of item being ordered
string	propName	The property we want to sort the query by

Returns

Type	Description
IQueryable	The original query modified to be ordered in descending order by the specified property

OrderByDescendingPropName<T>(IQueryable<T>, string)

Orders the specified query by the specified property name in descending order

Declaration

public static IQueryable<T> OrderByDescendingPropName<T>(this IQueryable<T> q, string propName)

Parameters

Type	Name	Description
IQueryable<T>	q	The query
string	propName	The property we want to sort the query by

Returns

Type	Description
IQueryable<T>	The original query modified to be ordered in descending order by the specified property

Type Parameters

Name	Description
T	The type of item being ordered

OrderByPropNameGeneric(IQueryable, Type, string)

Orders the specified query by the specified property name in ascending order

Declaration

public static IQueryable OrderByPropNameGeneric(this IQueryable q, Type type, string propName)

Parameters

Type	Name	Description
IQueryable	q	The query
Type	type	The type of item being ordered
string	propName	The property we want to sort the query by

Returns

Type	Description
IQueryable	The original query modified to be ordered in ascending order by the specified property

OrderByPropName<T>(IQueryable<T>, string)

Orders the specified query by the specified property name in ascending order

Declaration

public static IQueryable<T> OrderByPropName<T>(this IQueryable<T> q, string propName)

Parameters

Type	Name	Description
IQueryable<T>	q	The query
string	propName	The property we want to sort the query by

Returns

Type	Description
IQueryable<T>	The original query modified to be ordered in ascending order by the specified property

Type Parameters

Name	Description
T	The type of item being ordered

SetPropertyValue<T>(Expression<Func<T>>, T)

Sets the underlying properties value to the given value from an expression that contains the property

Declaration

public static void SetPropertyValue<T>(this Expression<Func<T>> lambda, T value)

Parameters

Type	Name	Description
Expression<Func<T>>	lambda	The expression
T	value	The value to set the property to

Type Parameters

Name	Description
T	The type of value to set

SetPropertyValue<In, T>(Expression<Func<In, T>>, T, In)

Sets the underlying properties value to the given value from an expression that contains the property

Declaration

public static void SetPropertyValue<In, T>(this Expression<Func<In, T>> lambda, T value, In input)

Parameters

Type	Name	Description
Expression<Func<In, T>>	lambda	The expression
T	value	The value to set the property to
In	input

Type Parameters

Name	Description
In	The input to the expression
T	The type of value to set

SkipGeneric(IQueryable, Type, int)

Alters the specified query to skip the specified number of items from the result set. Usually used in conjunction with order by.

Declaration

public static IQueryable SkipGeneric(this IQueryable q, Type type, int count)

Parameters

Type	Name	Description
IQueryable	q	The query to skip results from
Type	type	The type of items in this query
int	count	The amount of initial items to skip in the query results

Returns

Type	Description
IQueryable	The original query altered to skip the specified number of initial items from the query result set

TakeGeneric(IQueryable, Type, int)

Alters the specified query to only take the specified number of max items from the result set. Usually used in conjunction with order by.

Declaration

public static IQueryable TakeGeneric(this IQueryable q, Type type, int count)

Parameters

Type	Name	Description
IQueryable	q	The query to take a maximum number of results from
Type	type	The type of items in this query
int	count	The maximum amount of items to be returned by the query results

Returns

Type	Description
IQueryable	The original query altered to only return the specified number of maximum items from the query result set

ThenByDescendingPropNameGeneric(IQueryable, Type, string)

Orders the specified query by the specified property name in descending order after an initial order has already been applied

Declaration

public static IQueryable ThenByDescendingPropNameGeneric(this IQueryable q, Type type, string propName)

Parameters

Type	Name	Description
IQueryable	q	The query
Type	type	The type of item being ordered
string	propName	The property we want to sort the query by

Returns

Type	Description
IQueryable	The original query modified to be ordered in descending order by the specified property

ThenByDescendingPropName<T>(IQueryable<T>, string)

Orders the specified query by the specified property name in descending order after an initial order has already been applied

Declaration

public static IQueryable<T> ThenByDescendingPropName<T>(this IQueryable<T> q, string propName)

Parameters

Type	Name	Description
IQueryable<T>	q	The query
string	propName	The property we want to sort the query by

Returns

Type	Description
IQueryable<T>	The original query modified to be ordered in descending order by the specified property

Type Parameters

Name	Description
T	The type of item being ordered

ThenByPropNameGeneric(IQueryable, Type, string)

Orders the specified query by the specified property name in ascending order after an initial order has already been applied

Declaration

public static IQueryable ThenByPropNameGeneric(this IQueryable q, Type type, string propName)

Parameters

Type	Name	Description
IQueryable	q	The query
Type	type	The type of item being ordered
string	propName	The property we want to sort the query by

Returns

Type	Description
IQueryable	The original query modified to be ordered in ascending order by the specified property

ThenByPropName<T>(IQueryable<T>, string)

Orders the specified query by the specified property name in ascending order after an initial order has already been applied

Declaration

public static IQueryable<T> ThenByPropName<T>(this IQueryable<T> q, string propName)

Parameters

Type	Name	Description
IQueryable<T>	q	The query
string	propName	The property we want to sort the query by

Returns

Type	Description
IQueryable<T>	The original query modified to be ordered in ascending order by the specified property

Type Parameters

Name	Description
T	The type of item being ordered

Where<T>(string, SQLOperator, object, bool, bool)

Returns an expression that evaluates the specified where clause

Declaration

public static Expression<Func<T, bool>> Where<T>(string propName, SQLOperator op, object value, bool odataQuery, bool isCaseInsentive = false)

Parameters

Type	Name	Description
string	propName	The name of the property to compare in the expression
SQLOperator	op	The operation to perform to match the property and value in the expression
object	value	The value to compare to the property in the expression
bool	odataQuery	Indicates if the expression is running thorough an odata service - if it is the results are assumed to be case insensitive already
bool	isCaseInsentive

Returns

Type	Description
Expression<Func<T, bool>>	An expression that is the equivalent of this filter

Type Parameters

Name	Description
T	The type this expression works against

Remarks

For example:

public class MyItem
{
    public int Value { get; set; }
}

public class Example
{
    public void GetExpression()
    {
        var expr = ExpressionsHelper.Where<MyItem>(nameof(MyItem.Value), Database.SQLOperator.Equals, 5, odataQuery: false);
        //Is equivalent to the following:
        Expression<Func<MyItem, bool>> expr2 = x => x.Value == 5;
    }
}

Where<T>(string, string, SQLOperator, bool, bool)

Returns an expression that evaluates the specified where clause

Declaration

public static Expression<Func<T, bool>> Where<T>(string propName, string propName2, SQLOperator op, bool odataQuery, bool isCaseInsentive = false)

Parameters

Type	Name	Description
string	propName	The name of the property to compare in the expression
string	propName2	The name of the other property to compare in the expression
SQLOperator	op	The operation to perform to match the property and value in the expression
bool	odataQuery	Indicates if the expression is running thorough an odata service - if it is the results are assumed to be case insensitive already
bool	isCaseInsentive

Returns

Type	Description
Expression<Func<T, bool>>	An expression that is the equivalent of this filter

Type Parameters

Name	Description
T	The type this expression works against

Remarks

For example:

public class MyItem
{
    public int Value { get; set; }
    public int Value2 { get; set; }
}

public class Example
{
    public void GetExpression()
    {
        var expr = ExpressionsHelper.Where<MyItem>(nameof(MyItem.Value), nameof(MyItem.Value2), Database.SQLOperator.Equals, odataQuery: false);
        //Is equivalent to the following:
        Expression<Func<MyItem, bool>> expr2 = x => x.Value == x.Value2;
    }
}