如何从文件数组中读取搜索关键字的每个位置

Question

现在这是我的代码我只能找到该单词的最后位置。

    string[] textFiles = Directory.GetFiles(@"C:/PCRequestFiles");
    foreach (string fileName in textFiles)
    {
        string[] lines = File.ReadAllLines(fileName);

        for (int x = 0; x < lines.Length; x++)
        {
            int warnPos = lines[x].IndexOf(((TextBox)sm1.FindControl("Findtxt")).Text,
                          StringComparison.CurrentCultureIgnoreCase);

            if (warnPos > 0)
            {

                 ((Label)sm1.FindControl("Findlbl")).Text = "The data is in the File " + fileName.Substring(29) + " at line " + ( x + 1) + " ";               
                        dr = dt.NewRow();
                        dr["FileName"] = fileName.Substring(29);
                        dt.Rows.Add(dr);
                        gvFileGenStatus.DataSource = dt;
                        gvFileGenStatus.DataBind();

            }

        }
    }

提前感谢所有帮助。