Updating a data user using vb.net2008 and sql server management studio express

[jan princess]

please help me i'm trying to update a data user using vb.net2008 and sql server management studio express for my backend. the error says "must declare the scalar variable "@username" here's the code .

    Private Sub btnupdate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnupdate.Click
 
 
        Dim connstring = New SqlClient.SqlConnection("Data Source=MISD-ASBAUTISTA\SQLEXPRESS;Initial Catalog=inventory system;Integrated Security=SSPI;")
        Dim adapt = New SqlClient.SqlDataAdapter("select Username, Password from tbl_user", connstring)
        Dim dset As DataSet = New DataSet
        Dim cmdAdd As New SqlClient.SqlCommand()
        connstring.Open()
        cmdAdd.Connection = connstring
 
 
        cmdAdd.CommandText = "update username SET username = @username, password = @password, where tbl_user = @user"
 
 
        cmdAdd.ExecuteNonQuery() 'error within this line
 
        adapt.Fill(dset, "tbl_user")
        With DataGridView1
            .DataMember = "tbl_user"
            .DataSource = dset.DefaultViewManager
            .Update()
        End With
        MsgBox("Account has been updated!", MsgBoxStyle.Information, "SUCCESS")

please help me.. thank you :p

[MrMancunian]

Where do you declare @Username and how does it get its value? Did you write this yourself or did you copy/paste it? Check out this insight to find out how a query should look.

Steven