ERROR: use of unassigned local variable (for string array)

Question

I am reading connection strings from my App.config file and for that i have following code.

try
 {
    string[] dbnames;
    int counter = 0;
    foreach (ConnectionStringSettings connSettings in ConfigurationManager.ConnectionStrings) 
    {
        dbnames[counter] = connSettings.Name;
        counter++;
    }
    return dbnames;
 }
 catch
 {
    throw;
 }

this code giving me error use of unassigned local variable for dbnames. i will have multiple connection strings in my App.config. They can be none,1,2 and so on. Depending on the needs. so i cant statically assign the dbname size. Because there can be a scenario if they exceed the value of assigned size. eg. if i assign it a size of 5, and what if i get 6th connection string. and if i have 1, then remaining 4 will be a memory wastage.

If i am wrong then let me know.

Thanks.

Solution 1

Use this while initializing the array.

 string[] dbnames = new string[ConfigurationManager.ConnectionStrings.Count];

OR use List<string>

Solution 2

You can't resize a System.Array dynamically like that.

Fortunately, there's no reason to do so. Use a different type of collection, like a List<T> instead. (Make sure you've added a using declaration for the System.Collections.Generic namespace!)

Like an array, a List<T> allows you to access the elements in the list by index, but it's also dynamically resizable at run-time, which fulfills the requirements in your question. And of course, since it's a generic method, it has the additional advantage (as compared to some of your other choices) of being strongly-typed. Since you're working with string types, you would use List<string>.

EDIT: There's absolutely no need for that empty try/catch block. Why catch an exception if you're just going to immediately rethow it? Just let it bubble up. In general, you shouldn't catch exceptions unless and only unless you can fix their immediate cause.

Solution 3

You're declaring dbnames as a string array, but not defining it's size.

You'll need something like:

string[] dbames = new string[4];

where "4" is the length of your array.

If, however, you need a variable length you should use List<string>. In this case you can then add to it as necessary.

Solution 4

declare it after class e.g

i am also writing code and i used to always encounter this problem

   public class ABC{
string[] array;
ABC()
{
}
//your_function_logics
}

Solution 5

As others have said, you could just use a List<string>. I would use LINQ to do all of this though, if you're using .NET 3.5 or higher:

return ConfigurationManager.ConnectionStrings
                           .Cast<ConnectionStringSettings>()
                           .Select(setting => setting.Name)
                           .ToArray(); // Or ToList

• No need for a foreach loop (in your code - obviously it's there somewher :)
• You can easily decide whether to return a list, an array, or simply IEnumerable<string>
• No need for try/catch

View more solutions

Comments

[bitxwise]

+1 booota also didn't even initialize the array; he just declared it. And FYI, in case booota needs the return type to be string[], List<T> also has the ToArray() method - List<string> dbnames; dbnames.ToArray();

[booota]

How will i read app.config file which contains? [code]<?xml version="1.0" encoding="utf-8" ?> <configuration> <connectionStrings> <add name="Local Area Network" connectionString="server=localhost;User Id=root;database=myportfolio;connection timeout=30" /> </connectionStrings> </configuration> [/code]

[Adeel]

@booota you are already using ConfigurationManager class. With this you can read different section in the configuration file. e.g. in your foreach loop, you can use this code.ConfigurationManager.ConnectionStrings[i].ConnectionStr‌​ing

[booota]

but that i giving me some mdb information when i print the output. But i am connecting it to mysql using mysql connector. and my connection string is written above. as u can see.