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C#: Cannot implicitly convert type 'System.Collections.Generic.List<char>' to 'System.Collections.Generic.List<string>'

I would like to do some kind of console framework and for that I need command and arguments for the command. Here is part of my code:
string str = "I do not know how to fix this problem";
List<string> substringList = str.Split().ToList();
List<string> allArgsExcept1st = str[1..^0].ToList();
The input is type string.
The third line throws an error:
Cannot implicitly convert type 'System.Collections.Generic.List<char>' to 'System.Collections.Generic.List<string>'.
I am new to C# so I don't know what to think about this error and how to possibly fix it.
Thank you.

Based on your latest edit:
string str = "I do not know how to fix this problem";
List<string> substringList = str.Split().ToList();
List<string> allArgsExcept1st = str[1..^0].ToList();
The problem you have is here:
str[1..^0].ToList()
When you are using the range/slice function ([1..^0]) on your string you are, in return, getting a string. So calling ToList() on that string will give you a List<char> (since a string is also a IEnumerable<char>) but you are assigning it to a List<string>.
Its unclear what you are ultimately trying to do here, but to fix your problem you just need to change your last line to:
List<char> allArgsExcept1st = str[1..^0].ToList();

c# cannot implicitly convert type string [] to string

i tried to split the answer from the question in my quiz generator, here is my code
string test = questions = objReader.ReadLine().Split('?');
questions[qCounter] = questions[0];
answers[qCounter] = questions[1];
qCounter++;

this line is wrong because when you split a string, it return an array of string
string test = questions = objReader.ReadLine().Split('?');
then you should to do this:
string[] test = questions = objReader.ReadLine().Split('?');

I think the message is clear enough to identify the issue, as it says cannot implicitly convert type string [] to string. which means you are trying to assing a string[] to a string object. yes exactly that you did there.
The output of .Split() is a string[](RHS of the assignment), and the variable test is of type string. So its better to change the type of test as well as questions to string[] like the following:
string[] questions ;
string[] test = questions = objReader.ReadLine().Split('?');

Convert a String to a String[], splitted by characters in C# [duplicate]

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How to convert string type to string[] type in C#?

string[] is an array (vector) of strings
string is just a string (a list/array of characters)
Depending on how you want to convert this, the canonical answer could be:
string[] -> string
return String.Join(" ", myStringArray);
string -> string[]
return new []{ myString };

An array is a fixed collection of same-type data that are stored contiguously and that are accessible by an index (zero based).
A string is a sequence of characters.
Hence a String[] is a collection of Strings.
For example:
String foo = "Foo"; // one instance of String
String[] foos = new String[] { "Foo1", "Foo2", "Foo3" };
String firstFoo = foos[0]; // "Foo1"
Arrays (C# Programming Guide)
Edit: So obviously there's no direct way to convert a single String to an String[]
or vice-versa. Though you can use String.Split to get a String[] from a String by using a separator(for example comma).
To "convert" a String[] to a String(the opposite) you can use String.Join. You need to specify how you want to join those strings(f.e. with comma).
Here's an example:
var foos = "Foo1,Foo2,Foo3";
var fooArray = foos.Split(','); // now you have an array of 3 strings
foos = String.Join(",", fooArray); // now you have the same as in the first line

If you want to convert a string like "Mohammad" to String[] that contains all characters as String, this may help you:
"Mohammad".ToCharArray().Select(c => c.ToString()).ToArray()

You can create a string[] (string array) that contains your string like :
string someString = "something";
string[] stringArray = new string[]{ someString };
The variable stringArray will now have a length of 1 and contain someString.

To convert a string with comma separated values to a string array use Split:
string strOne = "One,Two,Three,Four";
string[] strArrayOne = new string[] {""};
//somewhere in your code
strArrayOne = strOne.Split(',');
Result will be a string array with four strings:
{"One","Two","Three","Four"}

zerkms told you the difference. If you like you can "convert" a string to an array of strings with length of 1.
If you want to send the string as a argument for example you can do like this:
var myString = "Test";
MethodThatRequiresStringArrayAsParameter( new[]{myString} );
I honestly can't see any other reason of doing the conversion than to satisty a method argument, but if it's another reason you will have to provide some information as to what you are trying to accomplish since there is probably a better solution.

string is a string, and string[] is an array of strings

A string is one string, a string[] is a string array. It means it's a variable with multiple strings in it.
Although you can convert a string to a string[] (create a string array with one element in it), it's probably a sign that you're trying to do something which you shouldn't do.

Casting can also help converting string to string[]. In this case, casting the string with ToArray() is demonstrated:
String myString = "My String";
String[] myString.Cast<char>().Cast<string>().ToArray();

A string holds one value, but a string[] holds many strings, as it's an array of string.
See more here

In case you are just a beginner and want to split a string into an array of letters but didn't know the right terminology for that is a char[];
String myString = "My String";
char[] characters = myString.ToCharArray();
If this is not what you were looking for, sorry for wasting your time :P

How to convert string to string array[] in c#

i have a string variable which receives data from web the data is in the from of string like this
string output="[1,2,3,4,5,6,7,8,9,0]";
i want to convert it into a string array [] so that i can specify each element via for each loop
string output;
into
string[] out;
PS: if any predefined method is there that will also help

You can do that using Trim And Split:
var out = output.TrimStart('[').TrimEnd(']').Split(',');
But your data looks like JSON string. So, if you are dealing with JSON instead of making your own parser try using libraries that already does that such as JSON.NET.

You can use Trim functions to remove brackets and then use Split() function to get the string array that contains the substrings in this string that are delimited by elements of a specified Unicode character.
var res = output.TrimStart('[')
.TrimEnd(']')
.Split(',');

string[] arr = output.Where(c => Char.IsDigit(c)).Select(c => c.ToString()).ToArray();

output.Substring(1, output.Length - 2).Split(',');

C# Cannot implicitly convert type 'string' to 'string[]' within an if else statement

I am trying to read a string into an array and I get the error "Cannot implecitly convert type 'string' to 'string[]'.
The error occurs here:
string[] sepText = result.Tables[0].Rows[0].Field<string>("WebHTML").UrlDecode();
My full if else statement is below:
if (!string.IsNullOrEmpty(result.Tables[0].Rows[0].Field<string>("WebHTML")))
{
string[] sepText = result.Tables[0].Rows[0].Field<string>("WebHTML").UrlDecode();
NewsContent.Text = sepText[1];
if (!string.IsNullOrEmpty(sepText[0]))
Image1.ImageUrl = sepText[0];
else
Image1.Visible = false;
NewsTitle.Text = String.Format("{3}", Extensions.GetServerName(true), result.Tables[0].Rows[0].Field<int>("News_Item_ID"), result.Tables[0].Rows[0].Field<string>("Title").UrlFormat(), result.Tables[0].Rows[0].Field<string>("Title"));
Hyperlink1.NavigateUrl = String.Format("{0}/news/{1}/{2}.aspx", Extensions.GetServerName(true), result.Tables[0].Rows[0].Field<int>("News_Item_ID"), result.Tables[0].Rows[0].Field<string>("Title").UrlFormat());
}
else
{
Hyperlink1.Visible = false;
Image1.Visible = false;
}
Thank you for your help!
EDIT Code for URL Decode:
public static string UrlDecode(this string str)
{
return System.Web.HttpUtility.UrlDecode(str);
}

result.Tables[0].Rows[0].Field<string>("WebHTML") is going to give you the value of the WebHTML field in the first row in the first table which is a single string rather than a string[].
You may want to show your code for UrlDecode() since it looks like a custom implementation rather than one of the built-in framework versions.
You also declare the UrlDecode method to take a string as a parameter and return a string. Remember, a string is not the same thing as a string array.

It seems that you are trying to put:
result.Tables[0].Rows[0].Field<string>("WebHTML").UrlDecode();
which returns a string, into an array of strings.
Simply delare your sepText variable as a string rather than a string array and you should be good to go, e.g.:
string sepText = result.Tables[0].Rows[0].Field<string>("WebHTML").UrlDecode();
Later in your code you will clearly need to read the contents of the string like this:
Image1.ImageUrl =sepText;

Assuming the UrlDecode you are using is the one from here then the result is a string and not a string[] !

UrlDecode returns a string and you are assigning it to an array.
If you want the parts you will have to use the string to create an Url object.
Url url = new Url(result.Tables[0].Rows[0].Field<string>("WebHTML"));
and then get the parts.
See: Get url parts without host

I don't think URLDecode works the way you think it works. All URLDecode does is remove URL encoding from a string. It does not return an array of strings - only the decoded value of the string you gave it.
http://msdn.microsoft.com/en-us/library/system.web.httputility.urldecode.aspx
Example: Your web browser replaces a space with %20. This changes the %20 back to a space.

That's because the result of this line is "string" and you're trying to assign it to an array since UrlDecode do not produce an array. What you probably wanted is to use a method split() to create an array of separators?