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Recently I have been developing web form application in ASP.NET (c#): I have an Image control:
<asp:Image ID="Avatar" runat="server" Height="225px" ImageUrl="~/Images/NoUser.jpg" Width="225px" />
And FileUpload & Button control
<asp:FileUpload ID="avatarUpload" runat="server" />
<asp:Button ID="btnUpload" runat="server" Text="Upload" OnClick="Upload" />
When user click button then "Upload" code is executed (the image is sent to the database). Problem is that I like to display the image which the user selected in Avatar Image controller before the user clicks "desperate" button.
Is that possible to do this automatically?
858
Steps: Create <img> element in the HTML code. Add style to <img> element and set display properties to none. Create a JavaScript “show()” function that can access the image and change the display property to block.
With the help of File Api of HTML5 (Example: Using files from web applications) you can accomplish this easily. Change the markup to use input type="file" instead of asp:FileUpload and add ID, add tag runat="server" to make it accessible from server. Your markup should look like:
<input ID="avatarUpload" type="file" name="file" onchange="previewFile()" runat="server" />
<%--<asp:FileUpload ID="avatarUpload" runat="server" />--%>
<asp:Button ID="btnUpload" runat="server" Text="Upload" OnClick="Upload" />
<asp:Image ID="Avatar" runat="server" Height="225px" ImageUrl="~/Images/NoUser.jpg" Width="225px" />
Now add a javascript function previewFile in the head of document:
<head runat="server">
<title></title>
<script type="text/javascript">
function previewFile() {
var preview = document.querySelector('#<%=Avatar.ClientID %>');
var file = document.querySelector('#<%=avatarUpload.ClientID %>').files[0];
var reader = new FileReader();
reader.onloadend = function () {
preview.src = reader.result;
}
if (file) {
reader.readAsDataURL(file);
} else {
preview.src = "";
}
}
</script>
</head>
Now after selecting an image you can see the preview like below:
You can use css to re-size it to a thumbnail. After clicking the Upload button, in the code you can find the posted file:
protected void Upload(object sender, EventArgs e)
{
int contentLength = avatarUpload.PostedFile.ContentLength;//You may need it for validation
string contentType = avatarUpload.PostedFile.ContentType;//You may need it for validation
string fileName = avatarUpload.PostedFile.FileName;
avatarUpload.PostedFile.SaveAs(@"c:\test.tmp");//Or code to save in the DataBase.
}
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