Expression.AddAssign Method (Expression, Expression)

Parameters

• left
  Type: System.Linq.Expressions.Expression
  An Expression to set the Left property equal to.

• right
  Type: System.Linq.Expressions.Expression
  An Expression to set the Right property equal to.

Return Value

Type: System.Linq.Expressions.BinaryExpression
A BinaryExpression that has the NodeType property equal to AddAssign and the Left and Right properties set to the specified values.

' Add the following directive to your file:
' Imports System.Linq.Expressions 

' The parameter expression is used to create a variable.
Dim variableExpr As ParameterExpression = Expression.Variable(GetType(Integer), "sampleVar")

' The block expression enables you to execute several expressions sequentually.
' In this block, the variable is first initialized with 1. 
' Then the AddAssign method adds 2 to the variable and assigns the result to the variable.
Dim addAssignExpr As BlockExpression = Expression.Block(
    New ParameterExpression() {variableExpr},
    Expression.Assign(variableExpr, Expression.Constant(1)),
    Expression.AddAssign(
        variableExpr,
        Expression.Constant(2)
    )
)

' Print the expression from the block expression.
outputBlock.Text &= "The expressions from the block expression:" & vbCrLf
For Each expr As Expression In addAssignExpr.Expressions
    outputBlock.Text &= expr.ToString() & vbCrLf
Next

outputBlock.Text &= "The result of executing the expression tree:" & vbCrLf
' The following statement first creates an expression tree,
' then compiles it, and then executes it.
outputBlock.Text &= Expression.Lambda(Of Func(Of Integer))(addAssignExpr).Compile()() & vbCrLf

' This code example produces the following output:
'
' The expressions from the block expression:
' (sampleVar = 1)
' (sampleVar += 2)

' The result of executing the expression tree:
' 3

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

// The Parameter expression is used to create a variable.
ParameterExpression variableExpr = Expression.Variable(typeof(int), "sampleVar");

// The block expression enables you to execute several expressions sequentually.
// In this bloc, the variable is first initialized with 1. 
// Then the AddAssign method adds 2 to the variable and assigns the result to the variable.
BlockExpression addAssignExpr = Expression.Block(
    new ParameterExpression[] { variableExpr },
    Expression.Assign(variableExpr, Expression.Constant(1)),
    Expression.AddAssign(
        variableExpr,
        Expression.Constant(2)
    )
);

// Print out the expression from the block expression.
outputBlock.Text += "The expressions from the block expression:" + "\n";
foreach (var expr in addAssignExpr.Expressions)
   outputBlock.Text += expr.ToString() + "\n";

outputBlock.Text += "The result of executing the expression tree:" + "\n";
// The following statement first creates an expression tree,
// then compiles it, and then executes it.
outputBlock.Text += Expression.Lambda<Func<int>>(addAssignExpr).Compile()() + "\n";

// This code example produces the following output:
//
// The expressions from the block expression:
// (sampleVar = 1)
// (sampleVar += 2)

// The result of executing the expression tree:
// 3