How to join int[] to a character separated string in .NET?

Question

I have an array of integers:

int[] number = new int[] { 2,3,6,7 };

What is the easiest way of converting these into a single string where

Answer 1

In .NET 4.0, string join has an overload for params object[], so it's as simple as:

int[] ids = new int[] { 1, 2, 3 };
string.Join(",", ids);

example

int[] ids = new int[] { 1, 2, 3 };
System.Data.Common.DbCommand cmd = new System.Data.SqlClient.SqlCommand("SELECT * FROM some_table WHERE id_column IN (@bla)");
cmd.CommandText = cmd.CommandText.Replace("@bla",  string.Join(",", ids));

In .NET 2.0, it's a tiny little bit more difficult, since there's no such overload. So you need your own generic method:

public static string JoinArray(string separator, T[] inputTypeArray)
{
    string strRetValue = null;
    System.Collections.Generic.List ls = new System.Collections.Generic.List();

    for (int i = 0; i < inputTypeArray.Length; ++i)
    {
        string str = System.Convert.ToString(inputTypeArray[i], System.Globalization.CultureInfo.InvariantCulture);

        if (!string.IsNullOrEmpty(str))
        { 
            // SQL-Escape
            // if (typeof(T) == typeof(string))
            //    str = str.Replace("'", "''");

            ls.Add(str);
        } // End if (!string.IsNullOrEmpty(str))

    } // Next i 

    strRetValue= string.Join(separator, ls.ToArray());
    ls.Clear();
    ls = null;

    return strRetValue;
}

In .NET 3.5, you can use extension methods:

public static class ArrayEx
{

    public static string JoinArray(this T[] inputTypeArray, string separator)
    {
        string strRetValue = null;
        System.Collections.Generic.List ls = new System.Collections.Generic.List();

        for (int i = 0; i < inputTypeArray.Length; ++i)
        {
            string str = System.Convert.ToString(inputTypeArray[i], System.Globalization.CultureInfo.InvariantCulture);

            if (!string.IsNullOrEmpty(str))
            { 
                // SQL-Escape
                // if (typeof(T) == typeof(string))
                //    str = str.Replace("'", "''");

                ls.Add(str);
            } // End if (!string.IsNullOrEmpty(str))

        } // Next i 

        strRetValue= string.Join(separator, ls.ToArray());
        ls.Clear();
        ls = null;

        return strRetValue;
    }

}

So you can use the JoinArray extension-method.

int[] ids = new int[] { 1, 2, 3 };
string strIdList = ids.JoinArray(",");

You can also use that extension method in .NET 2.0, if you add the ExtensionAttribute to your code:

// you need this once (only), and it must be in this namespace
namespace System.Runtime.CompilerServices
{
    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Method)]
    public sealed class ExtensionAttribute : Attribute {}
}