$(document).ready(function() {
    // 获取DropDownList元素
    var ddl = $('#<%= YourDropDownList.ClientID %>');
    
    // 临时存储原始AutoPostBack值
    var originalAutoPostBack = ddl.attr('autopostback');
    
    // 禁用AutoPostBack
    ddl.attr('autopostback', 'false');
    
    // 执行你的jQuery操作
    ddl.val('yourValue');
    
    // 恢复原始AutoPostBack设置
    ddl.attr('autopostback', originalAutoPostBack);
});

$(document).ready(function() {
    $('#<%= YourDropDownList.ClientID %>').change(function(e) {
        // 阻止事件冒泡和默认行为
        e.stopImmediatePropagation();
        e.preventDefault();
        
        // 执行你的操作
        console.log('Selected value changed to: ' + $(this).val());
    });
});

$(document).ready(function() {
    var ddl = $('#<%= YourDropDownList.ClientID %>');
    
    // 移除所有change事件处理程序
    ddl.off('change');
    
    // 添加你自己的处理程序
    ddl.change(function() {
        console.log('Selected value changed to: ' + $(this).val());
    });
});