I would like to know why my data is not saving permanently in my local database. If I close my application and open it again. I cannot download the uploaded data. Its showing an error called "The given key was not present in the dictionary” But I can download the file when the application is running. I mean, if the application is running and I upload a data to my grid, then i can download it without any error. If the application is closed and opened, that time if I try to download the same old file its throwing the error

My code

private void DownloadAttachment(DataGridViewCell dgvCell)
    {
        string fileName = Convert.ToString(dgvCell.Value);

        //Return if the cell is empty
        if (fileName == string.Empty)
            return;

        FileInfo fileInfo = new FileInfo(fileName);
        string fileExtension = fileInfo.Extension;

        byte[] byteData = null;

        //show save as dialog
        using (SaveFileDialog saveFileDialog1 = new SaveFileDialog())
        {
            //Set Save dialog properties
            saveFileDialog1.Filter = "Files (*" + fileExtension + ")|*" + fileExtension;
            saveFileDialog1.Title = "Save File as";
            saveFileDialog1.CheckPathExists = true;
            saveFileDialog1.FileName = fileName;

            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                cncInfoDataGridView.Rows[dgvCell.RowIndex].Cells[1].Value = fileInfo.Name;
                byteData = _myAttachments[dgvCell.RowIndex];
                File.WriteAllBytes(saveFileDialog1.FileName, byteData);
            }
        }
    }

Also if anybody could tell me a sample program to upload and download a file or document to/from the database.mdf and to view in
grid view with out using the sql server. because i dont want to use the sql server. Just using a local database.
Please anybody help me to find the right code.

Thanks in advance.

I am doing the worong thing now. I am now saving in a dictionary. which acts like a RAM. I need to zip it and save in database. For that i need help. Can you guys help me.

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