How to save SELECT sql query results in an array in C# Asp.net

Normally i use a class for this:

public class ClassName
{
    public string Col1 { get; set; }
    public int Col2 { get; set; }
}

Now you can use a loop to fill a list and ToArray if you really need an array:

ClassName[] allRecords = null;
string sql = @"SELECT col1,col2
               FROM  some table";
using (var command = new SqlCommand(sql, con))
{
    con.Open();
    using (var reader = command.ExecuteReader())
    {
        var list = new List<ClassName>();
        while (reader.Read())
            list.Add(new ClassName { Col1 = reader.GetString(0), Col2 = reader.GetInt32(1) });
        allRecords = list.ToArray();
    }
}

Note that i've presumed that the first column is a string and the second an integer. Just to demonstrate that C# is typesafe and how you use the DataReader.GetXY methods.

Instead of any Array you can load your data in DataTable like:

using System.Data;

DataTable dt = new DataTable();
using (var con = new SqlConnection("Data Source=local;Initial Catalog=Test;Integrated Security=True"))
{
    using (var command = new SqlCommand("SELECT col1,col2" +
    {
        con.Open();
        using (SqlDataReader dr = command.ExecuteReader())
        {
            dt.Load(dr);
        }
    }
}

You can also use SqlDataAdapater to fill your DataTable like

SqlDataAdapter da = new SqlDataAdapter(command);
da.Fill(dt);

Later you can iterate each row and compare like:

foreach (DataRow dr in dt.Rows)
{
    if (dr.Field<string>("col1") == "yourvalue") //your condition
    {
    }
}

Use a SQL DATA READER:

In this example i use a List instead an array.

try
{
    SqlCommand comm = new SqlCommand("SELECT CategoryID, CategoryName FROM Categories;",connection);
    connection.Open();

    SqlDataReader reader = comm.ExecuteReader();
    List<string> str = new List<string>();
    int i=0;
    while (reader.Read())
    {
        str.Add( reader.GetValue(i).ToString() );
        i++;
    }
    reader.Close();
}
catch (Exception)
{
    throw;
}
finally
{
    connection.Close();
}