You can build an expression tree which contains a break statement using Expression.Break method. For example, you have the following code.
int cValue = 5;
int cResult;
cResult = 1;
while (true)
{
if (cValue > 1)
{
cResult = cResult * cValue--;
}
else
{
break;
}
}
Console.WriteLine(cResult);
Here is the code that is required to build the same functionality using expression tree.
// Creating a parameter expression.
ParameterExpression value = Expression.Parameter(typeof(int), "value");
// Creating an expression to hold a local variable.
ParameterExpression result = Expression.Parameter(typeof(int), "result");
// Creating a label to jump to from a loop.
LabelTarget label = Expression.Label(typeof(int));
var ifThenElseExpr = Expression.IfThenElse(
// Condition: value > 1
Expression.GreaterThan(value, Expression.Constant(1)),
// If true: result *= value --
Expression.MultiplyAssign(result,
Expression.PostDecrementAssign(value)),
// If false, exit the loop and go to the label.
Expression.Break(label, result)
);
// Creating a method body.
BlockExpression block = Expression.Block(
// Adding a local variable.
new[] { result },
// Assigning a constant to a local variable: result = 1
Expression.Assign(result, Expression.Constant(1)),
// Adding a loop.
Expression.Loop(ifThenElseExpr, label)
);
// Compile and run an expression tree.
int factorial = Expression.Lambda<Func<int, int>>(block, value).Compile();
Console.WriteLine(factorial(5));