system out of memory exception is thrown

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C#

ASP.NET

I am retrieving bulk data from database and making changes in that data but it give me error outofmemoryexception. below is my code

public void AddArticleRefrences(ref List<Article> art)
{
    string blueWordStyle = "text-decoration: none; border-bottom: 1px solid #663366;color: #0000CC;";
    ArticalDAO objArt = new ArticalDAO();
    List<Article> MainArticle = objArt.GetListArticle(1);

    foreach (Article main in MainArticle)
    {
        foreach (var content in art)
        {
            content.Contents = Regex.Replace(content.Contents, main.Header, string.Format("<a href='{0}' target='_blank' style='{1}'>{2}</a>", "ViewArticle.aspx?Code=" + main.ArticleCode, blueWordStyle, main.Header));
        }
    }
}