Вы делаете это, читая байты загруженного файла в событии C1Upload1_Uploaded
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protected void C1Upload1_Uploaded(object sender, UploadedFileEventArgs e)
{
//Read uploaded file stream
C1FileInfo file = e.UploadedFile;
byte[] buffer = new byte[file.Size];
file.GetStream().Read(buffer, 0, file.Size);
file.GetStream().Close();
//Save file bytes to database
System.Data.SqlClient.SqlConnection sqlConn = new System.Data.SqlClient.SqlConnection("sqlConnectionString");
System.Data.SqlClient.SqlCommand sqlCmd = new System.Data.SqlClient.SqlCommand("INSET INTO yourtable(image) VALUES(@image)", sqlConn);
sqlCmd.Parameters.AddWithValue("@image", buffer);
sqlConn.Open();
sqlCmd.ExecuteNonQuery();
sqlConn.Close();
}