How can I read string value and store it in a array using data reader

Question

I am reading some list of values in the result but I am not sure where I am going wrong, I wont know the array size so I cant assign any value to it

string[] result = null;
while (reader.Read())
{
    result = Convert.ToString[](reader["RoleID"]);
}
reader.Close();

I am getting: Syntax error; value expected.

After I get the result value, how can I compare the values inside the result with a string? For example, I want to check whether the string check="Can send message"; is present in the result array or not. How can I do that?

You're not giving enough information for anyone to give you a practical answer. First off, your syntax is just wrong, you're iterating through the reader, trying to convert each value to the result array?? Depending on what you're trying to accomplish, there may be better ways to do this. — Random
– Random, Commented Nov 2, 2011 at 17:00

Anthony Pegram · Accepted Answer · 2011-11-02 17:01:19Z

3

Your code is syntactically wrong, hence the error. But when you have to build a collection of items but you do not know the size in advance, you want to use a List<T> as opposed to an array. The list will allow you to keep adding items.

var results = new List<string>();
while (reader.Read())
{
    results.Add(reader["RoleID"].ToString());
}

// results now holds all of the RoleID values in the reader

You can access the elements of the list via index, just like an array, and can query the list using Linq (also just like an array) if needed.

string check = "something";
if (results.Any(item => item.Equals(check)))
{
    // results contains the value in check 
}

// or use all items that equal check
foreach (var item in results.Where(obj => obj.Equals(check))
{
    // do something with each item that equals check
}

edited Nov 2, 2011 at 17:01

answered Nov 2, 2011 at 16:56

Anthony Pegram

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2 Comments

John Over a year ago

How to compare that with a string, I want to compare resutls with a string check="Something"

Anthony Pegram Over a year ago

Answer updated to show various querying techniques using Linq. (The same type of logic could be performed via explicit loops.)

huMpty duMpty · Accepted Answer · 2011-11-02 16:56:53Z

1

I preffer using ArrayList

var result= new ArrayList();
while (reader.Read())
        {
            result.Add(Convert.ToString[](reader["RoleID"]));
        }reader.Close();

answered Nov 2, 2011 at 16:56

huMpty duMpty

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2 Comments

Anthony Pegram Over a year ago

There is very little reason to use ArrayList if not tied to .NET 1.x / C# 1.x. With .NET / C# 2.0 or greater, List<T> is preferred.

Josh Campbell Over a year ago

I must side with @huMpty duMpty on this one. Although it may not be the best choice, it sure is easier to work with an ArrayList (from a beginners perspective, anyway).

james lewis · Accepted Answer · 2011-11-02 16:59:57Z

0

You should use a list as follows:

var results = new List<string>();
while( reader.Read() ){
    results.Add(reader["RoleID"].ToString());
}

Then you would iterate through all the strings in the collection and check them using a foreach statement:

foreach(var result in results) {
    if(result == "check") {
        // do something
    }
}

answered Nov 2, 2011 at 16:59

james lewis

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Comments

Mopthe · Accepted Answer · 2014-08-12 09:02:57Z

0

The list in Anthony Pegram's example can easily be converted to an array if needed.

string[] result = results.ToArray();

answered Aug 12, 2014 at 9:02

Mopthe

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