Question

下拉列表如何发现其选定的索引已更改，并需要触发选定的索引更改事件？

Suppose i have a dropdown which is bounded with objectdatasource and objectdatasource has following items opt1 opt2 opt3 opt4 then i added default value --select-- to objectdatasource, now dropdown is populated and i can see all the items on it. I have a button and on its client click, through java script i set opt4 to selected item. now if i select --select-- from dropdown then it does not fire selected index changed event but it fires dropdown s data bound event and then if i select any other value it fire both events and then if i again select --select-- then it fire both event, only first time if i select --select--then it will not fire selected index change event but if i select other than --select-- it fire both events.

所以我的问题是多普敦是如何发现它的选择指数发生了变化的。

Answer 1

如果includeStagesBeforeSyncPoint为true，则OnSelectedIndexChanged似乎应该始终在DropDownList回发时激发

System.Web.UI页面

private void ProcessRequestMain(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint) {
    if (includeStagesBeforeAsyncPoint) {
        ...
        if (this.IsPostBack) {
            ...
            this.RaiseChangedEvents();


internal void RaiseChangedEvents() {
    ...
    for (int i = 0; i < this._changedPostDataConsumers.Count; i++) {
        ...
        postBackDataHandler.RaisePostDataChangedEvent();
    }
}

System.Web.UI.WebControls.DropDownList系统

void IPostBackDataHandler.RaisePostDataChangedEvent()
{
    this.RaisePostDataChangedEvent();
}

protected virtual void RaisePostDataChangedEvent() {
    ..
    this.OnSelectedIndexChanged(EventArgs.Empty);
}

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