在GridView中要使成绩一列小于60字体展示红色时出错

在GridView中要使成绩一列小于60字体显示红色时出错
 代码如下：
   protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {  
            if (Convert.ToInt32(e.Row.Cells[6].Text.Trim()) <= 0
                  || Convert.ToInt32(e.Row.Cells[6].Text.Trim()) > 60)
            {
                e.Row.Cells[6].ForeColor = System.Drawing.Color.Red;
            } 
        }

提示输入字符串出错。

------解决方案--------------------
e.Row.Cells[6].Text.Trim()是整型的字符串嘛？
看看e.Row.Cells[6].Text.Trim()值是什么？

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)

  {

  string test=e.Row.Cells[6].Text.Trim();//看看这里的值是什么？

  if (e.Row.RowType == DataControlRowType.DataRow)

  {  

  if (Convert.ToInt32(e.Row.Cells[6].Text.Trim()) <= 0

  
------解决方案--------------------
 Convert.ToInt32(e.Row.Cells[6].Text.Trim()) < 60)

  {

  e.Row.Cells[6].ForeColor = System.Drawing.Color.Red;

  } 

  }

------解决方案--------------------

    <form id="form1" runat="server">

    <div>

        <asp:GridView ID="gv" runat="server" AutoGenerateColumns="false" onrowdatabound="gv_RowDataBound">

        <Columns>

            <asp:TemplateField>

                <ItemTemplate>

                    <asp:Label ID="lblGrade" runat="server" Text='<%#Eval("Grade") %>'></asp:Label>

                </ItemTemplate>

            </asp:TemplateField>

        </Columns>

        </asp:GridView>

    </div>

    </form>

    protected void Page_Load(object sender, EventArgs e)

    {

        if (!IsPostBack)

        {

            BindGrade();

        }

    }


    protected void BindGrade()