How to combine multiple string list with separator

Question

I have three string list, the purpose is combine these list to a single string with separator.

List<string> list1=new List<string>{"A","B","C"};
List<string> list2=new List<string>{"=","<", ">"};
List<string> list3=new List<string>{"1","2","3"};

The final output is like following:

A=1 AND B<2 AND C>3

Is there any easy way to generate the final string? I used for loop, but it seems to be ugly. I know C# string has Join method to combine an array with separator. How to combine multiple arrays with separator?

Below is my code:

StringBuilder str = new StringBuilder();
for(int i=0; i< list1.count; i++)
{
    str.AppendFormat("{0}{1}{2} AND ", list1[i], list2[i], list3[i]);
}
str.Length = str.Length -5;
string final = str.ToString();

I realise it doesn't really answer your question, but your problem might be more easily solved if the data was in a multi (2)-dimensional array; or your three lists were all contained inside a parent list — Paul Michaels
– Paul Michaels, Commented Mar 29, 2018 at 7:25
Using a for loop for this is absolutely fine. If you really think it looks too ugly you can still wrap it into a seperate method to "hide" the loop in your code. — Amelia B
– Amelia B, Commented Mar 29, 2018 at 7:27
You are using lists for everything? Why not a single List<Comparison> with properties for Operator, Variable and Value? No need to join multiple collections via index, that's most times a code smell that begs for refactoring. This class could override ToString to return what you ask for. — Tim Schmelter
– Tim Schmelter, Commented Mar 29, 2018 at 7:42
str.Length = str.Length -5; doesn't work str.Length is read only — fubo
– fubo, Commented Mar 29, 2018 at 8:20

fubo · Accepted Answer · 2018-03-29 07:40:19Z

24

Use Linq Zip() twice:

string result = string.Join(" AND ", list1.Zip(list2, (l1, l2) => l1 + l2).Zip(list3, (l2, l3) => l2 + l3));

https://dotnetfiddle.net/ZYlejS

edited Mar 29, 2018 at 7:40

answered Mar 29, 2018 at 7:27

fubo

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Comments

richej · Accepted Answer · 2018-03-29 07:27:36Z

10

You could use a combination of string.Join and linq:

string.Join(" AND ", list1.Select((e1, idx) => $"{e1} {list2[idx]} {list3[idx]}"));

answered Mar 29, 2018 at 7:27

richej

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1 Comment

Tim Schmelter Over a year ago

Just take care that all listst really have the same size.

HelloWorld · Accepted Answer · 2018-03-30 08:17:26Z

3

You could use one of overloads EquiZip() in MoreLINQ:

var res = string.Join(" AND ", list1.EquiZip(list2, list3, (x, y, z) => x + y + z));

answered Mar 30, 2018 at 8:17

HelloWorld

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Comments

Ousmane D. · Accepted Answer · 2018-03-29 22:10:28Z

1

You could also use a combination of string.Join along with Enumerable.Range like so:

string result = string.Join(" AND ", Enumerable.Range(0, Math.Min(list1.Count, 
                                    Math.Min(list2.Count, list3.Count)))
                      .Select(i => $"{list1[i]} {list2[i]} {list3[i]}"));

if the lists are guaranteed to have the same size then it can be reduced to:

string b = string.Join(" AND ", Enumerable.Range(0, list1.Count)
                 .Select(i => $"{list1[i]} {list2[i]} {list3[i]}"));

edited Mar 29, 2018 at 22:10

answered Mar 29, 2018 at 21:37

Ousmane D.

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