Improve the code for performance?
<p>I wrote the follow c# codes to generate a set of numbers and then compare with another set of numbers to remove the unwanted numbers. </p>

<p>But its taking too long at run time to complete the process. Following is the code behind file.</p>

<p>The numbers it has to generate is like 7 figures large and the numbers list which I use it as to remove is around 700 numbers.</p>

<p>Is there a way to improve the run time performance?</p>

<pre><code>string[] strAry = txtNumbersToBeExc.Text.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
    int[] intAry = new int[strAry.Length];
    List&lt;int&gt; intList = new List&lt;int&gt;();
    for (int i = 0; i &lt; strAry.Length; i++)
    {
        intList.Add(int.Parse(strAry[i]));
    }

    List&lt;int&gt; genList = new List&lt;int&gt;();

    for (int i = int.Parse(txtStartSeed.Text); i &lt;= int.Parse(txtEndSeed.Text); i++)
    {
        genList.Add(i);
    }
    lblStatus.Text += "Generated: " + genList.Capacity;

    var finalvar = from s in genList where !intList.Contains(s) select s;

    List&lt;int&gt; finalList = finalvar.ToList();

    foreach (var item in finalList)
    {
        txtGeneratedNum.Text += "959" + item + "\n";
    }
</code></pre>
