<asp:Repeater ID="Repeater1" runat="server" DataSourceID="SqlDataSource1" OnItemDataBound="Repeater1_ItemDataBound">
        <HeaderTemplate>
            <table align="center" class="tjqy" cellpadding="0" border="1" cellspacing="0" width="900">
                <tr>
        </HeaderTemplate>
        <ItemTemplate>
            <td>
                类型编号:<%#Eval("CategoryID") %><br />
                类型名称:<%#Eval("CategoryName")%>
            </td>
        </ItemTemplate>
        <FooterTemplate>
            </tr></table>
        </FooterTemplate>
    </asp:Repeater>
 <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"
        SelectCommand="SELECT * FROM [Categories]"></asp:SqlDataSource>

int i = 1;
    protected void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
        {
            if (i % 5 == 0)//这些的5为你每行显示的列数量
            {
                 e.Item.Controls.Add(new LiteralControl("</tr><tr>"));
                
            }
            i++;
        }
    }