我有一个在我的ASP.NET服务器控件中创建的HiddenField控件。 我为ValueChanged事件添加了一个新的EventHandler。HiddenField EventHandler ValueChanged在通过Javascript更改时未触发
当我的HiddenField的值从javascript函数中改变时,会触发此事件吗?
我遇到的主要问题是在值已更改或至少在回发之前尝试检索我的HiddenField服务器端的值。我在页面中有一个服务器控件,该页面包含一个导致回发的按钮,我最初尝试使用SaveControlState/LoadControlState,但由于某种原因,SaveControlState从未在回发发生之前调用。我需要能够从ValueChanged事件中或回发之前捕获值。
下面的代码:
public class ObjectTree : WebControl {
private CA.TreeView _treeView;
private HiddenField fldCheckedNodes = new HiddenField();
public CA.TreeView TreeView {
get { return _treeView; }
set { _treeView = value; }
}
public ObjectTree() {
_treeView = new CA.TreeView();
_treeView.ID = "objectTree";
fldCheckedNodes.ID = "fldCheckedNodes";
}
protected void fldCheckedNodes_ValueChanged(Object sender, EventArgs e) {
string test = fldCheckedNodes.Value;
}
protected override void OnPreRender(EventArgs e) {
TreeView.ClientSideOnNodeCheckChanged = TreeView.ClientID + "NodeChecked";
fldCheckedNodes.ValueChanged += new EventHandler(fldCheckedNodes_ValueChanged);
if (!Page.ClientScript.IsClientScriptBlockRegistered("jscript")) {
StringBuilder jscript = new StringBuilder();
jscript.AppendLine(" function " + TreeView.ClientID + "UpdateCheckedNodes() {");
jscript.AppendLine(" var x = 0;");
jscript.AppendLine(" var nodeArray = " + TreeView.ClientID + ".get_nodes().get_nodeArray();");
jscript.AppendLine(" var nodeLength = nodeArray.length;");
jscript.AppendLine(" document.getElementById('" + fldCheckedNodes.ClientID + "').value = \"\";");
jscript.AppendLine(" for (x=0; x < nodeLength; x++) {");
jscript.AppendLine(" examineNode(nodeArray[x]);");
jscript.AppendLine(" }");
jscript.AppendLine(" var result = document.getElementById('" + fldCheckedNodes.ClientID + "').value;");
jscript.AppendLine(" return true;");
jscript.AppendLine(" }");
jscript.AppendLine(" function examineNode(node) {");
jscript.AppendLine(" var y = 0;");
jscript.AppendLine(" var childNodes = node.get_nodes().get_nodeArray();");
jscript.AppendLine(" var childNodeLength = childNodes.length;");
jscript.AppendLine(" if (node.get_checked()) {");
jscript.AppendLine(" if (document.getElementById('" + fldCheckedNodes.ClientID + "').value.length > 0) {");
jscript.AppendLine(" document.getElementById('" + fldCheckedNodes.ClientID + "').value += \",\"; ");
jscript.AppendLine(" document.getElementById('" + fldCheckedNodes.ClientID + "').value += node.get_id();");
jscript.AppendLine(" } else {");
jscript.AppendLine(" document.getElementById('" + fldCheckedNodes.ClientID + "').value += node.get_id();");
jscript.AppendLine(" }");
jscript.AppendLine(" }");
jscript.AppendLine(" if (childNodeLength >= 1) {");
jscript.AppendLine(" for (y=0; y < childNodeLength; y++) {");
jscript.AppendLine(" examineNode(childNodes[y]);");
jscript.AppendLine(" }");
jscript.AppendLine(" } ");
jscript.AppendLine(" }");
jscript.AppendLine("</script>");
Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "jscript", jscript.ToString());
}
base.OnPreRender(e);
}
protected override void CreateChildControls() {
Controls.Add(TreeView);
Controls.Add(fldCheckedNodes);
}
protected override void RenderContents(HtmlTextWriter output) {
TreeView.RenderControl(output);
fldCheckedNodes.RenderControl(output);
}
}