Suppose I have a List<dynamic>
object containing strings:
var dlist = new List<dynamic>() { "test", "test2", "test3" };
Is there any efficient way of converting this into a proper List<string>
object? I know I can iterate over this list and cast each element to a string, then add this to the result list, but maybe some Linq magic could do the trick in one line?
I tried using some Select()
combined with ToList()
and Cast<string>
, but to no avail. How should this be done properly?
Note: By saying "efficient" I mean of course number of lines of code. I do not take execution time or performance into account. Also - let's suppose I do not need to type check, there will always be strings only in this dynamic list.
EDIT: Okay, so in regards to comments on "why Cast wasn't working for you" - looks like I had another problem regarding the data I receive (I'm using Dapper) and that's why it didn't work. Sorry for the confusion, I thought my list converting was wrong while the problem was not related to this.
Most likely the '?' is the ternary operator. Its grammar is: RESULT = (COND) ? ( STATEMEN IF TRUE) : (STATEMENT IF FALSE) It is a nice shorthand for the typical if-else statement: if (COND) { RESULT = (STATEMENT IF TRUE); } else { RESULT = (STATEMENT IF FALSE);
C operators are one of the features in C which has symbols that can be used to perform mathematical, relational, bitwise, conditional, or logical manipulations. The C programming language has a lot of built-in operators to perform various tasks as per the need of the program.
|= just assigns the bitwise OR of a variable with another to the one on the LHS.
Given
var dList = new List<dynamic>() { /*...initialize list */ };
If you are interested in extracting all the strings in the collection, ignoring all other types, you can use:
// Solution 1: Include only strings, no null values, no exceptions thrown var strings = dlist.OfType<string>().ToList();
If you are certain that all the items in the list are strings (it will throw an exception if they are not), you can use:
// Solution 2: Include strings with null values, Exception for other data types thrown var strings = dlist.Cast<string>().ToList();
If you want the default string representation, with null
for null
values, of all the items in the list, you can use:
// Solution 3: Include all, regardless of data type, no exceptions thrown var strings = dlist.Select(item => item?.ToString()).ToList();
This answer is for
dart/flutter
Given
List<dynamic> dList;
You can use
var sList = List<String>.from(dlist);
to convert a List<dynamic>
to List<String>
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