无法在GridView ASP.NET中设置列宽(GridView没有DataSource )

<div style="width: 500px;">
    <asp:GridView ID="GridView1" runat="server" CssClass="gridview">
        <!-- GridView的列定义 -->
    </asp:GridView>
</div>

<style>
    .gridview table {
        table-layout: fixed;
        width: 100%;
    }

    .gridview th, .gridview td {
        width: 100px; /* 设置列宽为100px */
    }
</style>

<asp:GridView ID="GridView1" runat="server">
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>
                <div style="width: 100px;">
                    <%# Eval("ColumnName") %>
                </div>
            </ItemTemplate>
        </asp:TemplateField>
        <!-- 其他列的定义 -->
    </Columns>
</asp:GridView>