The cast from type "DBNull" to type "Integer" is invalid

liuwei09314

A function is defined Public Function RunCard_Query(ByVal strtype As String, ByVal strdate As String, ByVal strclass As String) As DataSet
Dim data As New DataSet()
dsCommand.SelectCommand = New SqlCommand("SELECT MAX(CAST(SUBSTRING(RUNCARD,2,9) AS INTEGER)) AS NUM FROM RUNCARD WHERE TYPE ='" + strtype + "'AND CLASSNAME ='" + strclass + "'AND RUNCARD LIKE'" + strdate + "'+'%'", con)
'dsCommand.SelectCommand = New SqlCommand("SELECT COUNT(*) AS NUM FROM RUNCARD WHERE TYPE ='" + strtype + "'AND CLASSNAME ='" + strclass + "'AND RUNCARD LIKE'" + strdate + "'+ ' %'", con)
dsCommand.Fill(data)
RunCard_Query = data
End Function
Reference ds = mySqlData.RunCard_Query("Wafer_Lot", strdate, "PRO")
Dim i As Integer
Dim j As Integer

i = ds.Tables(0).Rows(0)("num")

j = i + 1
...
As a result, it says that the coercive conversion from type "DBNull" to type "Integer" is invalid. Please expert advice, urgent!!!

身材正

SELECT ISNULL(MAX(CAST(SUBSTRING(RUNCARD,2,9) AS INTEGER)),0) AS NUM FROM RUNCARD WHERE TYPE ...

身材正

ISNULL(...,0) as NUM

waxiaoning

j=iif(isdbnull(ds.Tables(0).Rows(0)("num")),0,ds.Tables(0).Rows(0)("num"))