Callback如何在Asp.net项目中使用

发布时间：2020-12-09 16:51:56 来源：亿速云阅读：154 作者：Leah 栏目：开发技术

Callback如何在Asp.net项目中使用？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。

.aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head runat="server"> 
<title>无标题页</title> 

<script type="text/javascript"> 

//向服务器传递参数 
function DoSearch(){ 
var firstName=document.getElementById("TextBox1").value; 
CallServer(firstName,""); 
} 

//得到服务器的数据 
function ReceiveServerData(txtUserInfo){ 
Results.innerHTML=txtUserInfo; 
} 

//设置每1秒执行一次 
setInterval("DoSearch()",1000); 
</script> 

</head> 
<body> 
<form id="form1" runat="server"> 
<div> 
姓名:<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> 
<br /> 
<span id="Results" ></span> 
</div> 
</form> 
</body> 
</html>
[/code]
.aspx.cs
[code]
using System; 
using System.Collections; 
using System.Configuration; 
using System.Data; 
using System.Web; 
using System.Web.Security; 
using System.Web.UI; 
using System.Web.UI.HtmlControls; 
using System.Web.UI.WebControls; 
using System.Web.UI.WebControls.WebParts; 
using System.Data.SqlClient; 

public partial class _Default : System.Web.UI.Page, ICallbackEventHandler 
{ 
protected string txtUserInfo; 


protected void Page_Load(object sender, EventArgs e) 
{ 
//获取一个对客户端函数的引用 
string cbReference = Page.ClientScript.GetCallbackEventReference(this, "arg", "ReceiveServerData", "context"); 
//动态注册回调函数 
string callbackScript = "function CallServer(arg,context)" + "{" + cbReference + "};"; 
//引发callbackScript 
Page.ClientScript.RegisterStartupScript(this.GetType(), "CallServer", callbackScript, true); 
} 

//引发Callback事件处理 
public void RaiseCallbackEvent(string txtFirstName) 
{ 
if (txtFirstName != null) 
{ 
String connString = System.Configuration.ConfigurationManager.ConnectionStrings["sqlserver2008"].ToString(); 

SqlConnection conn = new SqlConnection(connString); 

conn.Open(); 

SqlCommand comm = new SqlCommand("select * from zzx where [name]=@name", conn); 

comm.Parameters.Add("@name", SqlDbType.VarChar).Value = txtFirstName; 

SqlDataReader reader = comm.ExecuteReader(CommandBehavior.CloseConnection); 
if (reader.Read()) 
{ 
txtUserInfo = "员工编号:" + reader["id"].ToString() + "<br>"; 
txtUserInfo += "员工姓名:" + reader["name"].ToString() + "<br>"; 
txtUserInfo += "地址:" + reader["address"].ToString() + "<br>"; 
txtUserInfo += "服务器查询时间:" + DateTime.Now.ToString(); 
} 
else 
{ 
if (string.IsNullOrEmpty(txtFirstName)) 
{ 
txtUserInfo = "请输入姓名"; 
} 
else 
{ 
txtUserInfo = "查无此人"; 
} 
} 

comm.Dispose(); 
reader.Dispose(); 
conn.Dispose(); 
} 
} 

//得到回调的结果,返回给客户端 
public string GetCallbackResult() 
{ 
return txtUserInfo; 
} 


}

简化版(偷懒一下):

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head runat="server"> 
<title>无标题页</title> 

<script type="text/javascript"> 
function OnCallBack(txtUserInfo,context){ 
Results.innerHTML=txtUserInfo; 
} 
</script> 

</head> 
<body> 
<form id="form1" runat="server"> 
<div> 
姓名:<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> 
<input id="Button2" type="button" value="button" 
onclick="<%=Page.ClientScript.GetCallbackEventReference(this, "document.getElementById('TextBox1').value", "OnCallBack",null)%>" /> 
<br /> 
<span id="Results" ></span> 
</div> 
</form> 
</body> 
</html>
.aspx.cs

using System; 
using System.Collections; 
using System.Configuration; 
using System.Data; 
using System.Web; 
using System.Web.Security; 
using System.Web.UI; 
using System.Web.UI.HtmlControls; 
using System.Web.UI.WebControls; 
using System.Web.UI.WebControls.WebParts; 
using System.Data.SqlClient; 
using System.Text; 
public partial class _Default : System.Web.UI.Page, ICallbackEventHandler 
{ 
protected StringBuilder txtUserInfo; 

protected void Page_Load(object sender, EventArgs e) 
{ 

} 

public string GetCallbackResult() 
{ 
return txtUserInfo.ToString(); 
} 

public void RaiseCallbackEvent(string txtFirstName) 
{ 
txtUserInfo = new StringBuilder(); 
String connString = ConfigurationManager.ConnectionStrings["sqlserver2008"].ToString(); 
SqlConnection conn = new SqlConnection(connString); 
conn.Open(); 
SqlCommand comm = new SqlCommand("select * from zzx where [name]=@name", conn); 
comm.Parameters.Add("@name", SqlDbType.VarChar).Value = txtFirstName; 
SqlDataReader reader = comm.ExecuteReader(CommandBehavior.CloseConnection); 
if (reader.Read()) 
{ 
txtUserInfo.Append("员工编号:" + reader["id"].ToString() + "<br>"); 
txtUserInfo.Append("员工姓名:" + reader["name"].ToString() + "<br>"); 
txtUserInfo.Append("地址:" + reader["address"].ToString() + "<br>"); 
txtUserInfo.Append("查询时间:" + DateTime.Now.ToString()); 
} 
else 
{ 
if (txtFirstName == string.Empty) 
{ 
txtUserInfo.Append("请输入姓名"); 
} 
else 
{ 
txtUserInfo.Append("查无此人"); 
} 
reader.Dispose(); 
comm.Dispose(); 
conn.Dispose(); 
}
} 
}

示例3:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3" %> 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 

<html xmlns="http://www.w3.org/1999/xhtml"> 
<head runat="server"> 
<title>无标题页</title> 
<script type="text/javascript"> 
//客户端执行的方法 
//下面的方法是接收并处理服务器方法返回的结果 
function Success(args,context){ 
message.innerHTML=args; 
} 

//下面的方式是当接收服务器方法处理的结果发生异常时调用的方法 
function Error(){ 
message.innerHTML="发生了异常!"; 
} 
</script> 
</head> 
<body> 
<form id="form1" runat="server"> 
<div> 
用户名:<input type="text" id="txtUserName" onblur="CallServerMethod(txtUserName.value,null)" /> 
<span id="message"></span> 
<br /> 
密码:<input type="password" size="10" maxlength="20" id="txtPwd" /> 
</div> 
</form> 
</body> 
</html>
[code]
public partial class Default3 : System.Web.UI.Page,ICallbackEventHandler //实现ICallbackEventHandler接口 
{ 

String result = String.Empty; 

protected void Page_Load(object sender, EventArgs e) 
{ 
//获取当前页的ClientScriptManager的引用 
ClientScriptManager csm = Page.ClientScript; 
/*获取回调的引用.会在客户端生成WebForm_DoCallback方法, 
* 调用它来达到异步调用.这个方法是微软写的方法,会被发送 
到客户端*/ 
/*注意这里的"Success"和Error两个字符串分别是客户端代码中 
*定义的两个javascript函数*/ 
//下面的方法最后一个参数的意义:true表示执行异步回调,false标志执行同步回调 
String reference = csm.GetCallbackEventReference(this, "args", "Success", "", "Error", true); 
String callbackScript = "function CallServerMethod(args,context){\n"+ 
reference+";\n }"; 
//向当前页面注册javascript脚本代码 
csm.RegisterClientScriptBlock(this.GetType(), "CallServerMethod",callbackScript,true); 
} 

#region ICallbackEventHandler 成员 

/// <summary> 
/// 返回回调方法执行结果的方法 
/// </summary> 
public string GetCallbackResult() 
{ 
return result; 
} 

/// <summary> 
/// 在服务器端运行回调方法 
/// </summary> 
public void RaiseCallbackEvent(string eventArgument) 
{ 
if (eventArgument.ToLower().IndexOf("admin")!=-1) 
{ 
result =eventArgument+ "不能作为用户注册."; 
} 
else 
{ 
result = eventArgument + "可以注册."; 
} 
} 

#endregion 
}

看完上述内容，你们掌握Callback如何在Asp.net项目中使用的方法了吗？如果还想学到更多技能或想了解更多相关内容，欢迎关注亿速云行业资讯频道，感谢各位的阅读！

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