Handle errors used in VB6

Will error capture affect the speed?

Yes, using error handling will reduce some performance. Net, using Try Catch will also affect the performance. Therefore, when we use Reflector to decompile Microsoft class libraries, we will find that its sub-process rarely uses Try to capture errors, generally, you can use predictable methods to determine possible errors and handle them accordingly.

In fact, after error capture is used, the compiled code actually does a lot of operations that we don't know about. Although it facilitates the encoding process to a certain extent, but it sacrifices a certain speed, which has advantages and disadvantages. Therefore, we should use error capture correctly.

Tested VB6 code

　　

Option Explicit

　　

Dim cn As New ADODB. Connection

Dim rs As New ADODB. Recordset

Dim m_FldsName () As String

　　

Private Sub commandementclick ()

　　

Dim II As Long

Dim t As Single

　　

Cn. Open "Provider = SQLOLEDB.1; Persist Security Info = False; User ID = sa; Initial Catalog = guangshang; Data Source = SUPER"

Rs. Open "Select * from FldSet", cn, adOpenKeyset

　　

Do Until rs. EOF = True

Rs. MoveNext

Loop

　　

Rs. MoveFirst

T = Timer

　　

ReDim m_FldsName (rs. Fields. Count)

For II = 0 To rs. Fields. Count-1

M_FldsName (II) = rs. Fields (II). Name

Next

　　

Do Until rs. EOF = True

ReadFieldsNotOnErr "Err1"

ReadFieldsNotOnErr "TableName"

ReadFieldsNotOnErr "Err2"

Rs. MoveNext

Loop

MsgBox "NotErr:" & Timer-t

On Error Resume Next

Rs. MoveFirst

T = Timer

Do Until rs. EOF = True

ReadFieldsOnErr "Err1"

ReadFieldsOnErr "TableName"

ReadFieldsOnErr "Err2"

Rs. MoveNext

Loop

MsgBox "OnErr:" & Timer-t

　　

Rs. Close

Cn. Close

　　

End Sub

　　

Private Sub ReadFieldsOnErr (FieldName As String)

Dim v As Variant

V = rs (FieldName). Value

End Sub

　　

Private Sub ReadFieldsNotOnErr (FieldName As String)

Dim II As Long

Dim IsExists As Boolean

Dim v As Variant

IsExists = False

　　

For II = 0 To UBound (m_FldsName)-1

If m_FldsName (II) = FieldName Then

IsExists = True

Exit

End If

Next

　　

If IsExists = True Then

V = rs (FieldName). Value

End If

End Sub

　　

==========================================

　　

Test results:

No error

ReadFieldsOnErr: 0. 46

ReadFieldsNotOnErr: 0. 47

Incorrect

ReadFieldsOnErr: 0.96

ReadFieldsNotOnErr: 0.47

We can see that error handling is not used, and the speed is quite stable. When error handling is used, the speed gap is large when errors exist. Therefore, we recommend that you pre-process possible errors in subprocesses that are frequently called in loops to reduce the use of On error to increase the speed.