/// <summary>
/// Combines the sequence of expressions using the specified binary operator.
/// </summary>
/// <param name="expressions">A sequence of expressions to combine.</param>
/// <param name="op">The <see cref="BinaryOperator" /> to use when combining.</param>
/// <returns>An instance of <see cref="Expression" /> that represents the combination of all the expressions in the sequence.</returns>
/// <remarks>
/// When the sequence is empty, null is returned.
/// When the sequence contains a single expression, that expression is returned.
/// In all other cases, all expressions are combined in a chain of instances of <see cref="BinaryOperationExpression" />.
/// Null values in the sequence are replaced with instances of <see cref="NullExpression" />.
/// </remarks>
public static Expression Combined(this IEnumerable<Expression> expressions, BinaryOperator op)
{
Expression result = null;
foreach (Expression expression in expressions.WithConvertedNulls())
{
if (result == null)
{
result = expression;
}
else
{
result = new BinaryOperationExpression(result, expression, op);
}
}
return result;
}