Callback如何在Asp.net項目中使用

發布時間：2020-12-09 16:51:56 來源：億速云閱讀：154 作者：Leah 欄目：開發技術

Callback如何在Asp.net項目中使用？相信很多沒有經驗的人對此束手無策，為此本文總結了問題出現的原因和解決方法，通過這篇文章希望你能解決這個問題。

.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>無標題頁</title> 

<script type="text/javascript"> 

//向服務器傳遞參數 
function DoSearch(){ 
var firstName=document.getElementById("TextBox1").value; 
CallServer(firstName,""); 
} 

//得到服務器的數據 
function ReceiveServerData(txtUserInfo){ 
Results.innerHTML=txtUserInfo; 
} 

//設置每1秒執行一次 
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) 
{ 
//獲取一個對客戶端函數的引用 
string cbReference = Page.ClientScript.GetCallbackEventReference(this, "arg", "ReceiveServerData", "context"); 
//動態注冊回調函數 
string callbackScript = "function CallServer(arg,context)" + "{" + cbReference + "};"; 
//引發callbackScript 
Page.ClientScript.RegisterStartupScript(this.GetType(), "CallServer", callbackScript, true); 
} 

//引發Callback事件處理 
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 = "員工編號:" + reader["id"].ToString() + "<br>"; 
txtUserInfo += "員工姓名:" + reader["name"].ToString() + "<br>"; 
txtUserInfo += "地址:" + reader["address"].ToString() + "<br>"; 
txtUserInfo += "服務器查詢時間:" + DateTime.Now.ToString(); 
} 
else 
{ 
if (string.IsNullOrEmpty(txtFirstName)) 
{ 
txtUserInfo = "請輸入姓名"; 
} 
else 
{ 
txtUserInfo = "查無此人"; 
} 
} 

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

//得到回調的結果,返回給客戶端 
public string GetCallbackResult() 
{ 
return txtUserInfo; 
} 


}

簡化版(偷懶一下):

<%@ 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>無標題頁</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("員工編號:" + reader["id"].ToString() + "<br>"); 
txtUserInfo.Append("員工姓名:" + reader["name"].ToString() + "<br>"); 
txtUserInfo.Append("地址:" + reader["address"].ToString() + "<br>"); 
txtUserInfo.Append("查詢時間:" + DateTime.Now.ToString()); 
} 
else 
{ 
if (txtFirstName == string.Empty) 
{ 
txtUserInfo.Append("請輸入姓名"); 
} 
else 
{ 
txtUserInfo.Append("查無此人"); 
} 
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>無標題頁</title> 
<script type="text/javascript"> 
//客戶端執行的方法 
//下面的方法是接收并處理服務器方法返回的結果 
function Success(args,context){ 
message.innerHTML=args; 
} 

//下面的方式是當接收服務器方法處理的結果發生異常時調用的方法 
function Error(){ 
message.innerHTML="發生了異常!"; 
} 
</script> 
</head> 
<body> 
<form id="form1" runat="server"> 
<div> 
用戶名:<input type="text" id="txtUserName" onblur="CallServerMethod(txtUserName.value,null)" /> 
<span id="message"></span> 
<br /> 
密碼:<input type="password" size="10" maxlength="20" id="txtPwd" /> 
</div> 
</form> 
</body> 
</html>
[code]
public partial class Default3 : System.Web.UI.Page,ICallbackEventHandler //實現ICallbackEventHandler接口 
{ 

String result = String.Empty; 

protected void Page_Load(object sender, EventArgs e) 
{ 
//獲取當前頁的ClientScriptManager的引用 
ClientScriptManager csm = Page.ClientScript; 
/*獲取回調的引用.會在客戶端生成WebForm_DoCallback方法, 
* 調用它來達到異步調用.這個方法是微軟寫的方法,會被發送 
到客戶端*/ 
/*注意這里的"Success"和Error兩個字符串分別是客戶端代碼中 
*定義的兩個javascript函數*/ 
//下面的方法最后一個參數的意義:true表示執行異步回調,false標志執行同步回調 
String reference = csm.GetCallbackEventReference(this, "args", "Success", "", "Error", true); 
String callbackScript = "function CallServerMethod(args,context){\n"+ 
reference+";\n }"; 
//向當前頁面注冊javascript腳本代碼 
csm.RegisterClientScriptBlock(this.GetType(), "CallServerMethod",callbackScript,true); 
} 

#region ICallbackEventHandler 成員 

/// <summary> 
/// 返回回調方法執行結果的方法 
/// </summary> 
public string GetCallbackResult() 
{ 
return result; 
} 

/// <summary> 
/// 在服務器端運行回調方法 
/// </summary> 
public void RaiseCallbackEvent(string eventArgument) 
{ 
if (eventArgument.ToLower().IndexOf("admin")!=-1) 
{ 
result =eventArgument+ "不能作為用戶注冊."; 
} 
else 
{ 
result = eventArgument + "可以注冊."; 
} 
} 

#endregion 
}

看完上述內容，你們掌握Callback如何在Asp.net項目中使用的方法了嗎？如果還想學到更多技能或想了解更多相關內容，歡迎關注億速云行業資訊頻道，感謝各位的閱讀！

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