FileUpLoad控件

</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Image ID="Image" runat="server" width="50" Height="50"/>
        <br />
        <asp:TextBox ID="info" runat="server"></asp:TextBox>
        <br />
 
        <asp:FileUpload ID="up" runat="server" />
        <br/>
        <asp:Button ID="btnupLoad" runat="server" Text="Button" 
            onclick="btnupLoad_Click" />
    </div>
    </form>
</body>
</html>

后套代码：

protected void btnupLoad_Click(object sender, EventArgs e)
    {
        if (up.HasFile)
        {
            if (up.PostedFile.ContentType.Substring(0, 5) == "image")
            {
                try
                {
                    string serverPath = Server.MapPath("upLoad");
                    if (!System.IO.Directory.Exists(serverPath))
                    {
                        System.IO.Directory.CreateDirectory(serverPath);
                    }
                    string imgName = up.FileName;
                    string newPath = serverPath + "\" + imgName;
                    up.SaveAs(newPath);
                    ClientScript.RegisterStartupScript(this.GetType(), "", "alert('上传成功');", true);
                    info.Text = "";
                    Image.ImageUrl = "upLoad/" + imgName;
                    info.Text += "路径：" + up.PostedFile.ContentType;
                }
                catch
                {
                    ClientScript.RegisterStartupScript(this.GetType(), "", "alert('上传失败');", true);
                }
            }
            else
            {
                ClientScript.RegisterStartupScript(this.GetType(), "", "alert('请选择图片');", true);
            }
        }
        else
        {
            ClientScript.RegisterStartupScript(this.GetType(), "", "alert('选择要上传的图片');", true);
        }
    }

ClientScript.RegisterStartupScript(this.GetType(), "", "alert('请选择图片');", true);

若是gif图像，则ContentType的值为image/gif