VB.net save a picture to a SQL Server database (i)

server| Data | Database preparation knowledge: STREAM, ado.net



Microsoft's SQL Server database image, text and other fields are binary large objects. These objects are accessed slightly differently from other lightweight objects. For example, when we open a datasheet, common types of fields can be seen, but the image type of the field is not, can only be read programmatically. This piece of information is about how to use VB. NET to the SQL Server database to store pictures, how to remove picture browsing from the database. I also spent the boss's energy here, mainly to answer a classmate's questions. His inquisitive way of learning, I was anxious out of a cold sweat, ashamed ... ）



This routine uses SQL Server's own Northwind database, where employees (staff) datasheet has a field "photo", which is used to store photos, there are 9 records, I spent half a day trying to see the 9 people picture, is invisible. It is now speculated that the photo of these people are simply empty. So I decided to add some new records.



In this routine, I implemented a simple WinForm program that selects a picture file (BMP or JPG) by clicking the "Open" button and displays it in the graphics control PictureBox. Save to the database by using the saving button. Click the "View" checkbox to switch to the browse state and watch the image stored in the database.


The System.IO namespace of the Microsoft. NET Framework provides us with a FileStream file stream class. We can use this file stream to easily read and write binary large objects. Because of the flow operation used for binary large objects, it is universal for any file. You can also do this by reading and writing text files.

Steps:

1, first look at the Northwind database Employees table structure


2, know the method of. NET connection SQL Server, do not know, look at my written "ado.net in the Connection object" bar. It's OK to read the following sentences:

Dim Conn As New SqlConnection ("server=localhost;database=northwind;integrated security=true;"

Dim Sqlcomm as New SqlCommand

Sqlcomm. Connection = conn

Sqlcomm.commandtext = "INSERT into employees (Lastname,firstname,photo) VALUES (@lastname, @firstname, @photo)"

Dim Prm1 as New SqlParameter ("@lastname", Txtln.text)

Dim Prm2 as New SqlParameter ("@firstname", Txtfn.text)

Dim prm3 as New SqlParameter ("@photo", SqlDbType.VarBinary, Int (FS). Length), _ ParameterDirection.Input, False, 0, 0, "", DataRowVersion.Current, Data)

Sqlcomm. Parameters.Add (PRM1)

Sqlcomm. Parameters.Add (PRM2)

Sqlcomm. Parameters.Add (PRM3)




3, create a new Windows application form, the interface is as follows: (Figure 1)