Expression.ArrayAccess Method

Definition

Namespace:

System.Linq.Expressions

Assemblies:

netstandard.dll, System.Linq.Expressions.dll

Creates an IndexExpression to access an array.

Overloads

ArrayAccess(Expression, IEnumerable<Expression>)	Creates an IndexExpression to access a multidimensional array.
ArrayAccess(Expression, Expression[])	Creates an IndexExpression to access an array.

ArrayAccess(Expression, IEnumerable<Expression>)

Source:

IndexExpression.cs

Creates an IndexExpression to access a multidimensional array.

C#

public static System.Linq.Expressions.IndexExpression ArrayAccess(System.Linq.Expressions.Expression array, System.Collections.Generic.IEnumerable<System.Linq.Expressions.Expression>? indexes);

Parameters

array

Expression

An expression that represents the multidimensional array.

indexes

IEnumerable<Expression>

An IEnumerable<T> containing expressions used to index the array.

Returns

IndexExpression

The created IndexExpression.

Examples

The following code example shows how to change the value of an element in a multidimensional array by using the ArrayAccess method.

C#

// Add the following directive to your file:
// using System.Linq.Expressions;

// This parameter expression represents a variable that will hold the two-dimensional array.
ParameterExpression arrayExpr = Expression.Parameter(typeof(int[,]), "Array");

// This parameter expression represents a first array index.
ParameterExpression firstIndexExpr = Expression.Parameter(typeof(int), "FirstIndex");
// This parameter expression represents a second array index.
ParameterExpression secondIndexExpr = Expression.Parameter(typeof(int), "SecondIndex");

// The list of indexes.
List<Expression> indexes = new List<Expression> { firstIndexExpr, secondIndexExpr };

// This parameter represents the value that will be added to a corresponding array element.
ParameterExpression valueExpr = Expression.Parameter(typeof(int), "Value");

// This expression represents an access operation to a multidimensional array.
// It can be used for assigning to, or reading from, an array element.
Expression arrayAccessExpr = Expression.ArrayAccess(
    arrayExpr,
    indexes
);

// This lambda expression assigns a value provided to it to a specified array element.
// The array, the index of the array element, and the value to be added to the element
// are parameters of the lambda expression.
Expression<Func<int[,], int, int, int, int>> lambdaExpr =
    Expression.Lambda<Func<int[,], int, int, int, int>>(
        Expression.Assign(arrayAccessExpr, Expression.Add(arrayAccessExpr, valueExpr)),
        arrayExpr,
        firstIndexExpr,
        secondIndexExpr,
        valueExpr
);

// Print out expressions.
Console.WriteLine("Array Access Expression:");
Console.WriteLine(arrayAccessExpr.ToString());

Console.WriteLine("Lambda Expression:");
Console.WriteLine(lambdaExpr.ToString());

Console.WriteLine("The result of executing the lambda expression:");

// The following statement first creates an expression tree,
// then compiles it, and then executes it.
// Parameters passed to the Invoke method are passed to the lambda expression.
int[,] sampleArray = { {10,  20,   30},
                       {100, 200, 300}};
Console.WriteLine(lambdaExpr.Compile().Invoke(sampleArray, 1, 1, 5));

// This code example produces the following output:
//
// Array Access Expression:
// Array[FirstIndex, SecondIndex]

// Lambda Expression:
// (Array, FirstIndex, SecondIndex Value) =>
// (Array[FirstIndex, SecondIndex] = (Array[FirstIndex, SecondIndex] + Value))

// The result of executing the lambda expression:
// 205

Remarks

The expression that represents the array can be obtained by using the MakeMemberAccess method, or through NewArrayBounds or NewArrayInit.

ArrayAccess(Expression, Expression[])

Source:

IndexExpression.cs

Creates an IndexExpression to access an array.

C#

public static System.Linq.Expressions.IndexExpression ArrayAccess(System.Linq.Expressions.Expression array, params System.Linq.Expressions.Expression[]? indexes);

Parameters

array

Expression

An expression representing the array to index.

indexes

Expression[]

An array that contains expressions used to index the array.

Returns

IndexExpression

The created IndexExpression.

Examples

The following code example shows how to change a value of an array element by using the ArrayAccess method.

C#

// Add the following directive to your file:
// using System.Linq.Expressions;

// This parameter expression represents a variable that will hold the array.
ParameterExpression arrayExpr = Expression.Parameter(typeof(int[]), "Array");

// This parameter expression represents an array index.
ParameterExpression indexExpr = Expression.Parameter(typeof(int), "Index");

// This parameter represents the value that will be added to a corresponding array element.
ParameterExpression valueExpr = Expression.Parameter(typeof(int), "Value");

// This expression represents an array access operation.
// It can be used for assigning to, or reading from, an array element.
Expression arrayAccessExpr = Expression.ArrayAccess(
    arrayExpr,
    indexExpr
);

// This lambda expression assigns a value provided to it to a specified array element.
// The array, the index of the array element, and the value to be added to the element
// are parameters of the lambda expression.
Expression<Func<int[], int, int, int>> lambdaExpr = Expression.Lambda<Func<int[], int, int, int>>(
    Expression.Assign(arrayAccessExpr, Expression.Add(arrayAccessExpr, valueExpr)),
    arrayExpr,
    indexExpr,
    valueExpr
);

// Print out expressions.
Console.WriteLine("Array Access Expression:");
Console.WriteLine(arrayAccessExpr.ToString());

Console.WriteLine("Lambda Expression:");
Console.WriteLine(lambdaExpr.ToString());

Console.WriteLine("The result of executing the lambda expression:");

// The following statement first creates an expression tree,
// then compiles it, and then executes it.
// Parameters passed to the Invoke method are passed to the lambda expression.
Console.WriteLine(lambdaExpr.Compile().Invoke(new int[] { 10, 20, 30 }, 0, 5));

// This code example produces the following output:
//
// Array Access Expression:
// Array[Index]

// Lambda Expression:
// (Array, Index, Value) => (Array[Index] = (Array[Index] + Value))

// The result of executing the lambda expression:
// 15

Remarks

The expression that represents the array can be obtained by using the MakeMemberAccess method, or through NewArrayBounds or NewArrayInit.

For multidimensional arrays, use the ArrayAccess method.