public static Expression <Func <TSource, TResult> > Combine <TSource, TResult>(this IEnumerable <Expression <Func <TSource, TResult> > > expresions, Func <Expression, Expression, Expression> combineOperator)
{
ParameterExpression parameter = null;
Expression resultBody = null;
foreach (var expression in expresions)
{
if (resultBody == null)
{
resultBody = expression.Body;
parameter = expression.Parameters[0];
}
else
{
Expression expressionBody = expression.Body;
ParameterExpression expressionParameter = expression.Parameters[0];
var rebinder = new ParameterRebinder(expressionParameter, parameter);
expressionBody = rebinder.Visit(expressionBody);
resultBody = combineOperator(resultBody, expressionBody);
}
}
if (resultBody == null)
{
throw new ArgumentException("Expressions Enumerable is empty", "expresions");
}
return(Expression.Lambda <Func <TSource, TResult> >(resultBody, parameter));
}
internal static Expression ReplaceParameter(this Expression sourceExpression, ParameterExpression replaceParam, ParameterExpression parameter)
{
ExpressionVisitor rebinder = new ParameterRebinder(replaceParam, parameter);
return(rebinder.Visit(sourceExpression));
}
