Unable to change foreach to LINQ syntax

Question

I am trying unsuccessfully to change the following loop to a LINQ expression:

int index = 0;
IList<IWebElement> divNota = new List<IWebElement>();

foreach (IWebElement element in tablaNotas)
{
    divNota.Add(element.FindElement(By.Id("accion-1-celda-0-" + index + "-0")));
    index++;
}

I tried using

IList <IWebElement> divNota = tablaNotas.Select(element => element.FindElement(By.Id("accion-1-celda-0-"+ tablaNotas.IndexOf(element) + "-0"))).ToList();

But tablaNotas.IndexOf(element)always returns -1, meaning the element was not found inside tablaNotas.

The string "accion-1-celda-0-"+ tablaNotas.IndexOf(element) + "-0" is meant to change to

"accion-1-celda-0-"+ 1 + "-0"
"accion-1-celda-0-"+ 2 + "-0"
"accion-1-celda-0-"+ 3 + "-0"
...
"accion-1-celda-0-"+ n + "-0"

In accordance to element's index

Any help is appreciated

There is a select overload where you can get the current index. Have a look here: https://stackoverflow.com/a/18108850/2961887 — ErazerBrecht, Oct 28 '18 at 21:44

score 5 · Answer 1 · answered Oct 29 '18 at 07:36

In Linq some reserved word like Where, FirstOrDefault create a condition for your query and the Select reserved word can create your object that you want the Select method applies a method to elements. It is an elegant way to modify the elements in a collection such as an array. This method receives as a parameter an anonymous function—typically specified as a lambda expression.

Example: Let's look at a program where the Select extension method is applied to a string array. A local variable of array type is allocated and three string literals are used. We use Select on this array reference.

The basic method are here:

public static System.Collections.Generic.IEnumerable<TResult> Select<TSource,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,int,TResult> selector);

Now! for this issue that you searched for that you can use of this code:

var divNotaResult = list
            .Select((data, index) => data.FindElement(By.Id("accion-1-celda-0-" + index + "-0")))
            .ToList();

In Select method do like foreach we have tow object in function data and index.

The data have each data in loop, and the index have count of loop.

score 4 · Accepted Answer · answered Oct 28 '18 at 21:41

4

            var result = tableNotas
            .Select((element, index) => element.FindElement(By.Id("accion-1-celda-0-" + index + "-0")))
            .ToList();

answered Oct 28 '18 at 21:41

Szymon Tomczyk

1,219
11
16

Wow, this works perfectly. Could you point me to documentation about the index parameter in `(element, index)`? Thanks a lot! – elgato Oct 28 '18 at 21:44
3

@elgato: See https://learn.microsoft.com/en-gb/dotnet/api/system.linq.enumerable.select?view=netframework-4.7#System_Linq_Enumerable_Select__2_System_Collections_Generic_IEnumerable___0__System_Func___0_System_Int32___1__ – Jon Skeet Oct 28 '18 at 21:45

score 3 · Answer 3 · answered Oct 28 '18 at 21:42

3

Use this:

var divNota = 
    tablaNotas.Select((element, index) => 
        element.FindElement(By.Id($"accion-1-celda-0-{index}-0")))
    .ToList();

answered Oct 28 '18 at 21:42

Kirill Polishchuk

54,804
11
122
125

Unable to change foreach to LINQ syntax

3 Answers3