How to delete a row in sql using vb.net - sql

Question

Sorry if its easy or basic i am brand new to sql and tables so im just trying to figure it out
Basically im trying to delete a row that the user selects
By having them click on a row then clicking a delete button but i don't know how that should look ive tried a few different ways but none of them seem to work.
No error comes up but it just dosen't delete the row
Private Sub DeleteSelectedUsers()
Dim connection As SqlConnection = New SqlConnection()
connection.ConnectionString = "Data Source=GERARD-PC\SQLEXPRESS; Initial Catalog=TestDB;User ID=AccountsUser;Password=password123"
connection.Open()
Dim adp As SqlDataAdapter = New SqlDataAdapter _
("Delete * from dgrdUsers.SelectedRows(0).Cells", connection)
End Sub
Private Sub btnDelete_Click(sender As Object, e As EventArgs) Handles btnDelete.Click
Try
Dim username As String = dgrdUsers.SelectedRows(0).Cells.Item("Username").Value.ToString()
If (MessageBox.Show(Me, "Do you want to delete user " & username & "?", "Confirm Delete", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = DialogResult.Yes) Then
DeleteSelectedUsers()
End If
Catch ex As Exception
End Try
End Sub
Any ideas?

Answer 1

The syntax required to delete a row in the database table requires at least three parts.
The DELETE command
The FROM statement to identify the table where the delete action should occur
The WHERE condition to identify the record (or records) to delete
So it is a string like this: DELETE FROM tablename WHERE condition
and applied to your code you get this.
Private Sub DeleteSelectedUsers(userName as String)
Using connection As SqlConnection = New SqlConnection()
connection.ConnectionString = "...."
connection.Open()
Dim cmd As SqlCommand = New SqlCommand _
("DELETE FROM Table WHERE userName = #user", connection)
cmd.Parameters.Add("#user", SqlDbType.NVarChar).Value = userName
cmd.ExecuteNonQuery()
End Using
End Sub
(Table and UserName are fantasy names because we don't know what is the actual schema of your database)
Other things I have changed:
The connection is created inside a using block to be sure a proper
closure and dispose happens even in case of errors
The name of the user to remove should be passed as parameter to the
function
No need to use an adapter when you just need to execute a single
SqlCommand
The query doesn't concatenate strings to build the command but use a
parameter added to the command itself and specifying a type for the
data matching the type on the database table