First, you should load the image file to Dynamic Web TWAIN. Currently, we only ensure that images created by Dynamic Web TWAIN or Dynamic TWAIN can be loaded successfully.

You can use the LoadImage method or the LoadImageEx method to load the image file to Dynamic Web TWAIN. Before acquiring images, please check the value of the IfAppendImage property. If it is true, the new scanned image will be appended after the last image in buffer (the default value of this property is true). Click here if you want to insert new scanned images to an existing multi-page file.

Code (C#):

private void Load_Click(object sender, EventArgs e)
{
      axDynamicWebTwain1.MaxImagesInBuffer = 4;
      //the maximum number of images can be held in buffer in the trial version is 4
      axDynamicWebTwain1.LoadImage("G:\\wwwroot\\a.tif");
}

private void Add_Click(object sender, EventArgs e)
{
      axDynamicWebTwain1.OpenSource();
      axDynamicWebTwain1.SelectSource();
      axDynamicWebTwain1.IfAppendImage = true;
      axDynamicWebTwain1.AcquireImage();
 }

Reference:

LoadImage  LoadImageEx  IfAppendImage  AcquireImage