Question

将VB.NET 的LINQ改成C#版本

Public Function ContainsExpression(Of TElement, TValue)(ByVal valueSelector As System.Linq.Expressions.Expression(Of Func(Of TElement, TValue)), ByVal values As IEnumerable(Of TValue)) As System.Linq.Expressions.Expression(Of Func(Of TElement, Boolean))
If valueSelector Is Nothing Then
Throw New ArgumentNullException("valueSelector")
End If
If values Is Nothing Then
Throw New ArgumentNullException("values")
End If
Dim p As System.Linq.Expressions.ParameterExpression = valueSelector.Parameters.Single()

If Not values.Any() Then Return Function(e) False

Dim equals = values.Select(Function(value) DirectCast(System.Linq.Expressions.Expression.Equal(valueSelector.Body, System.Linq.Expressions.Expression.Constant(value, GetType(TValue))), System.Linq.Expressions.Expression))
Dim body = equals.Aggregate(Function(accumulate, equal) System.Linq.Expressions.Expression.Or(accumulate, equal))

Return System.Linq.Expressions.Expression.Lambda(Of Func(Of TElement, Boolean))(body, p)
End Function

Answer 1

public System.Linq.Expressions.Expression<Func<TElement, bool>> ContainsExpression<TElement, TValue>(System.Linq.Expressions.Expression<Func<TElement, TValue>> valueSelector, IEnumerable<TValue> values)
{
if (valueSelector == null)
{
throw new ArgumentNullException("valueSelector");
}
if (values == null)
{
throw new ArgumentNullException("values");
}
System.Linq.Expressions.ParameterExpression p = valueSelector.Parameters.Single();
if (!values.Any())
return e => false;
var @equals = values.Select(value => (System.Linq.Expressions.Expression)System.Linq.Expressions.Expression.Equal(valueSelector.Body, System.Linq.Expressions.Expression.Constant(value, typeof(TValue))));
var body = @equals.Aggregate((accumulate, equal) => System.Linq.Expressions.Expression.Or(accumulate, equal));
return System.Linq.Expressions.Expression.Lambda<Func<TElement, bool>>(body, p);
}

Answer 2

public System.Linq.Expressions.Expression<Func<TElement, bool>> ContainsExpression<TElement, TValue>(System.Linq.Expressions.Expression<Func<TElement, TValue>> valueSelector, IEnumerable<TValue> values)
        {
            if (valueSelector == null)
            {
                throw new ArgumentNullException("valueSelector");
            }
            if (values == null)
            {
                throw new ArgumentNullException("values");
            }
            System.Linq.Expressions.ParameterExpression p = valueSelector.Parameters.Single();
            if (!values.Any())
                return e => false;
            var @equals = values.Select(value => (System.Linq.Expressions.Expression)System.Linq.Expressions.Expression.Equal(valueSelector.Body, System.Linq.Expressions.Expression.Constant(value, typeof(TValue))));
            var body = @equals.Aggregate((accumulate, equal) => System.Linq.Expressions.Expression.Or(accumulate, equal));
            return System.Linq.Expressions.Expression.Lambda<Func<TElement, bool>>(body, p);
        }