Comparing database values with values from a GridView

I have a block of C# code here that stores data to an ArrayList from the database and compares each with the values from the GridView.

Is there a way to reduce the line of code and improve its readability?

while (DataReader.Read())
{
    arrHostName.Add(DataReader.GetString(0));
    arrUsers.Add(DataReader.GetString(2));
    arrPSName.Add(DataReader.GetString(3));
}           
foreach (Infragistics.Win.UltraWinGrid.UltraGridRow row in Grid2.Rows)
{
    string rowHostName = row.Cells["HostName"].Value.ToString();
    string rowUsers = row.Cells["Users"].Value.ToString();
    string rowPSName= row.Cells["PS_NAME"].Value.ToString();

    foreach (string a in arrHostName)
    {
        if (rowHostName == a.ToString())
        { 
            row.Appearance.BackColor = Color.Yellow;
            row.Appearance.FontData.Bold = Infragistics.Win.DefaultableBoolean.True;
        }
    }
    foreach (string a in arrUsers)
    {
        if (rowUsers == a.ToString())
        {
            row.Appearance.BackColor = Color.Yellow;
            row.Appearance.FontData.Bold = Infragistics.Win.DefaultableBoolean.True;
        }
    }
    foreach (string a in arrPSName)
    {
        if (rowPSName == a.ToString())
        {
            row.Appearance.BackColor = Color.Yellow;
            row.Appearance.FontData.Bold = Infragistics.Win.DefaultableBoolean.True;
        }
    }
}

It looks like what you want is ArrayList.Contains.

string rowHostName = row.Cells["HostName"].Value.ToString();
string rowUsers = row.Cells["Users"].Value.ToString();
string rowPSName= row.Cells["PS_NAME"].Value.ToString();

if (arrHostName.Contains(rowHostName) 
    || arrUsers.Contains(rowUsers) 
    || arrPSName.Contains(rowPSName))
{ 
    row.Appearance.BackColor = Color.Yellow;
    row.Appearance.FontData.Bold = Infragistics.Win.DefaultableBoolean.True;
}

And if you only use the collections above to check if they contain some values, you should prefer HashSet over ArrayList.

Of course, you should then change the names of the local variables accordingly, from arrHostName to hostNames and so on. It is always better not to clutter variable names with type information in C#, whose type system is good enough.

StackExchange Code Review Q#27074, answer score: 8