Client-Callback非同步数据查询

本文介绍了一个使用ASP.NET实现客户端回调功能的例子。通过按钮点击触发JavaScript回调,将输入框中的内容传递给服务器进行处理,并更新页面显示结果。

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页面代码:

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title></title>
<script type="text/JavaScript">
function OnCallback(txtUserInfo, context) {
document.getElementById(
"Results").innerText = txtUserInfo;
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<h2>
Client
-Callback非同步数据查询</h2>
姓名:
<input id="txtUserName" type="text" />
<input id="btnCallback" type="button"
value
="Callback" onclick="<%= ClientScript.GetCallbackEventReference(this,"document.getElementById('txtUserName').value","OnCallback",null) %>" /><br />
<div id="Results" style="background-color: pink">
</div>
</div>
</form>
</body>
</html>

后台代码:

    public partial class WebForm1 : System.Web.UI.Page, System.Web.UI.ICallbackEventHandler
{
protected string txtUserInfo; //用户基本数据
protected void Page_Load(object sender, EventArgs e)
{

}

public string GetCallbackResult()
{
return txtUserInfo;
}

public void RaiseCallbackEvent(string eventArgument)
{
if (eventArgument != null)
{
//SqlConnection conn = new SqlConnection("data source=.;initial catalog=Northwind;user id=sa;password=missoft");
//conn.Open();

//SqlCommand cmd = new SqlCommand("select EmployeeID,FirstName,City,Address from Employees where FirstName=@FirstName", conn);
//cmd.Parameters.Add("@FirstName", SqlDbType.NVarChar, 10).Value = eventArgument;
//SqlDataReader dr = cmd.ExecuteReader();

//if (dr.Read())
//{
// txtUserInfo = "员工编号:" + dr["EmployeeID"] + "\r\n";
// txtUserInfo += "姓名:" + dr["FirstName"] + "\r\n";
// txtUserInfo += "居住城市:" + dr["City"] + "\r\n";
// txtUserInfo += "地址:" + dr["Address"].ToString().Replace("\r\n", "") + "\r\n";
// txtUserInfo += "服务器查询时间:" + DateTime.Now.ToLongTimeString();
//}
//else
//{
if (String.IsNullOrEmpty(eventArgument))
{
txtUserInfo
= "请输入姓名";
}
else
{
txtUserInfo
= "查无此人!";
}
//}
}
}
}

转载于:https://www.cnblogs.com/qiuweiguo/archive/2011/08/04/2127398.html

/** * @file * @brief Implements the functionality of MQTT-C. * @note The only files that are included are mqtt.h and mqtt_pal.h. * * @cond Doxygen_Suppress */ enum MQTTErrors mqtt_sync(struct mqtt_client *client) { /* Recover from any errors */ enum MQTTErrors err; int reconnecting = 0; MQTT_PAL_MUTEX_LOCK(&client->mutex); if (client->error != MQTT_ERROR_RECONNECTING && client->error != MQTT_OK && client->reconnect_callback != NULL) { client->reconnect_callback(client, &client->reconnect_state); if (client->error != MQTT_OK) { client->error = MQTT_ERROR_RECONNECT_FAILED; /* normally unlocked during CONNECT */ MQTT_PAL_MUTEX_UNLOCK(&client->mutex); } err = client->error; if (err != MQTT_OK) return err; } else { /* mqtt_reconnect will have queued the disconnect packet - that needs to be sent and then call reconnect */ if (client->error == MQTT_ERROR_RECONNECTING) { reconnecting = 1; client->error = MQTT_OK; } MQTT_PAL_MUTEX_UNLOCK(&client->mutex); } /* Call inspector callback if necessary */ if (client->inspector_callback != NULL) { MQTT_PAL_MUTEX_LOCK(&client->mutex); err = client->inspector_callback(client); MQTT_PAL_MUTEX_UNLOCK(&client->mutex); if (err != MQTT_OK) return err; } /* Call receive */ err = (enum MQTTErrors)__mqtt_recv(client); if (err != MQTT_OK) return err; /* Call send */ err = (enum MQTTErrors)__mqtt_send(client); /* mqtt_reconnect will essentially be a disconnect if there is no callback */ if (reconnecting && client->reconnect_callback != NULL) { MQTT_PAL_MUTEX_LOCK(&client->mutex); client->reconnect_callback(client, &client->reconnect_state); } return err; }
03-17
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