HtmlInputFile.OnPreRender メソッドとは? わかりやすく解説

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HtmlInputFile.OnPreRender メソッド

HtmlInputFile コントロールの PreRender イベント発生させます

名前空間: System.Web.UI.HtmlControls
アセンブリ: System.Web (system.web.dll 内)
構文構文

Protected Friend Overrides
 Sub OnPreRender ( _
    e As EventArgs _
)
Dim e As EventArgs

Me.OnPreRender(e)
protected internal override void OnPreRender
 (
    EventArgs e
)
protected public:
virtual void OnPreRender (
    EventArgs^ e
) override
protected void OnPreRender (
    EventArgs e
)
protected internal override function
 OnPreRender (
    e : EventArgs
)

パラメータ

e

イベント データ格納している EventArgs。

解説解説
使用例使用例

OnPreRender メソッドオーバーライドして、それぞれのカスタムHtmlInputFile コントロールに常に Title 属性追加されるようにする方法次のコード例示します。この例を正常に動作させるには、コンピュータの C: ドライブTemp というディレクトリ作成する必要があります

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB.Controls"
 Assembly="Samples.AspNet.VB"
 %>
<%@ Page Language="VB" AutoEventWireup="True"
 %>

<script runat="server">
  
  Sub Button1_Click(ByVal source As
 Object, ByVal e As EventArgs)

    ' Make sure the file was submitted.  
    If HtmlInputText1.Value = ""
 Then
      
      Span1.InnerHtml = "Error: You must enter a file name."
    
    ' Save the file 
    ElseIf Not (HtmlInputFile1.PostedFile Is
 Nothing) Then

      Try
        
        HtmlInputFile1.PostedFile.SaveAs("c:\\temp\\"
 & HtmlInputText1.Value)
        Span1.InnerHtml = "File uploaded successfully to: <b>c:\temp\"
 _
                        & HtmlInputText1.Value & "</b>
 on the Web server."

      Catch exc As Exception
        
        Span1.InnerHtml = "Error saving <b>c:\temp\"
 _
                        & HtmlInputText1.Value & "</b><br>"
 _
                        & exc.ToString() & "."
        
      End Try
      
    End If
    
  End Sub
  
</script>

<html>
  <head>
    <title>Custom HtmlInputFile OnPreRender Example</title>
  </head>

  <body>
    <form enctype="multipart/form-data"
          runat="server">

      <h3>Custom HtmlInputFile OnPreRender Example</h3>

      Select File to Upload:
      <aspSample:CustomHtmlInputFileOnPreRender
        id="HtmlInputFile1"
        type="file"
        runat="server"
        name="HtmlInputFile1">

      <p>
      Save as file name (no path):
      <input id="HtmlInputText1"
        type="text"
        runat="server"
        name="Text1">

      </p>
      <p>
      <span id="Span1"
        style="font: 8pt verdana;"
        runat="server" />

      </p>
      <p>
      <input type="button"
        id="Button1"
        value="Upload"
        onserverclick="Button1_Click"
        runat="server"
        name="Button1">

      </p>

    </form>

  </body>
</html>
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls"
 Assembly="Samples.AspNet.CS" %>
<%@ Page Language="C#" AutoEventWireup="True" %>

<script runat="server">

  void Button1_Click(object Source, EventArgs e)
  {
    // Make sure a file was submitted.
    if (HtmlInputText1.Value == "")
    {
      
      Span1.InnerHtml = "Error: You must enter a file name.";
      
    }
      
    // Save the file.
    else if (HtmlInputFile1.PostedFile != null)
    {  
      try
      {
        
        HtmlInputFile1.PostedFile.SaveAs("c:\\temp\\" + HtmlInputText1.Value);
        Span1.InnerHtml = "File uploaded successfully to: <b>c:\\temp\\"
 + 
                           HtmlInputText1.Value + "</b> on the Web server.";
               
      }
      catch (Exception exc)
      {
        
        Span1.InnerHtml = "Error saving <b>c:\\temp\\" +
                           HtmlInputText1.Value + "</b><br>"
 + exc.ToString() + ".";
        
      }
      
    }
    
  }
</script>

<html>
  <head>
    <title>Custom HtmlInputFile OnPreRender Example</title>
  </head>
  <body>
    <form enctype="multipart/form-data"
          runat="server">

      <h3>Custom HtmlInputFile OnPreRender Example</h3>
 
      Select File to Upload:
      <aspSample:CustomHtmlInputFileOnPreRender
        id="HtmlInputFile1"
        type="file"
        runat="server"
        name="HtmlInputFile1">

      <p>
      Save as file name (no path):
      <input id="HtmlInputText1"
        type="text"
        runat="server"
        name="Text1">

      </p>
      <p>
      <span id="Span1"
        style="font: 8pt verdana;"
        runat="server" />

      </p>
      <p>
      <input type="button"
        id="Button1"
        value="Upload"
        onserverclick="Button1_Click"
        runat="server"
        name="Button1">

      </p>

    </form>

  </body>
</html>
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.JSL.Controls"
 Assembly="Samples.AspNet.JSL" %>
<%@ Page Language="VJ#" AutoEventWireup="True" %>
<HTML>
  <HEAD>
    <title>Custom HtmlInputFile - OnPreRender - VJ# Example</title>
    <script runat=server>
void Button1_Click(Object source, EventArgs e)
{
    if (HtmlInputText1.get_Value().Equals("")) {
        Span1.set_InnerHtml("Error: you must enter a file name");
    }
    else if (HtmlInputFile1.get_PostedFile()
 != null) {
        String tempPath = Environment.GetFolderPath(Environment.SpecialFolder.
            InternetCache) + "\\";
        try {
            HtmlInputFile1.get_PostedFile().SaveAs(tempPath + HtmlInputText1.
                get_Value());
            Span1.set_InnerHtml("File uploaded successfully to:<br><b>"
                + tempPath + HtmlInputText1.get_Value()
                + "</b><br>on the Web server");
        }
        catch (Exception ex) {
            Span1.set_InnerHtml("Error saving file:<br><b>"
                + tempPath + HtmlInputText1.get_Value() + "</b><br>"
                + ex.ToString());
        }
    }
} //Button1_Click
    </script>
  </HEAD>
  <body>
    <form id="Form1" method="post" runat="server"
 enctype="multipart/form-data">

      <h3>Custom HtmlInputFile - OnPreRender - VJ# Example</h3>

      Select File to Upload:
      <aspSample:CustomHtmlInputFileOnPreRender
        id="HtmlInputFile1"
        type="file"
        runat="server"
        name="HtmlInputFile1">
      </p>

      <p>
      Save as filename (no path):
      <input id="HtmlInputText1"
        type="text"
        runat="server"
        name="Text1">
      </p>
      <p>
      <span id="Span1"
        style="font: 8pt verdana;"
        runat="server" />
      </p>
      <p>
      <input type="button"
        id="Button1"
        value="Upload"
        OnServerClick="Button1_Click"
        runat="server"
        name="Button1">
      </p>

    </form>
  </body>
</HTML>
Imports System.Web
Imports System.Security.Permissions

Namespace Samples.AspNet.VB.Controls

    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)>
 _
    Public NotInheritable Class
 CustomHtmlInputFileOnPreRender
        Inherits System.Web.UI.HtmlControls.HtmlInputFile

        Protected Overrides Sub
 OnPreRender(ByVal e As System.EventArgs)

            ' Call the base OnPreRender method.
            MyBase.OnPreRender(e)

            ' Add a Title attribute to the HtmlInputFile control.
            Me.Attributes.Add("title",
 "Click the Browse button to select a file to upload.")
        End Sub
    End Class

End Namespace
using System.Web;
using System.Security.Permissions;

namespace Samples.AspNet.CS.Controls
{
    [AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
    public sealed class CustomHtmlInputFileOnPreRender
 : System.Web.UI.HtmlControls.HtmlInputFile
    {
        protected override void OnPreRender(System.EventArgs
 e)
        {
            // Call the base OnPreRender method.
            base.OnPreRender(e);
            
            // Add a Title attribute to the HtmlInputFile control.
            this.Attributes.Add("title", "Click
 the Browse button to select a file to upload.");
        }
    }
}
package Samples.AspNet.JSL.Controls;

public class CustomHtmlInputFileOnPreRender
    extends System.Web.UI.HtmlControls.HtmlInputFile
{
    protected void OnPreRender(System.EventArgs
 e)
    {
        // Call the base OnPreRender method.
        super.OnPreRender(e);
        // Add a Title attribute to HtmlInputFile.
        this.get_Attributes().Add("title", 
            "Click the Browse button to select a file to upload.");
    } //OnPreRender
} //CustomHtmlInputFileOnPreRender
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参照参照
関連項目
HtmlInputFile クラス
HtmlInputFile メンバ
System.Web.UI.HtmlControls 名前空間
HtmlForm クラス
HtmlForm.Enctype プロパティ
Control.OnPreRender
Control.PreRender
その他の技術情報
HTML サーバー コントロール



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