Dim conn As New SqlConnection(connectionString)

Dim sql As String = "update table1 set value1 = @value where pkvalue = @pk"
Dim cmd As New SqlCommand(sql, conn)

cmd.Parameters.AddWithValue("@value", TextBox1.Text)
cmd.Parameters.AddWithValue("@pk", primaryKeyValue)

conn.Open()
cmd.ExecuteNonQuery()
conn.Close()