Operator '=' is not defined for type 'Integer' and type 'DBNull'.

Question

User-1106823036 posted

My scenario goes like this: I have sections (section1- section2-...)

for each section there are classes(section1:class1- class2, section2:class1,...)

I want to display for each section its own classes.

here is my db structure:

table: Sections                      table:classes


Id | sections                        Id | sectionId | class
-------------
 1 | section1                        1  |     1     | class1
 2 | section2                        2  |     1     | class2
                                     3  |     2     | class1

here is what I am trying to do

 <%
                Dim tb As SQLExec = New SQLExec
                Dim sql As String
                Dim DS As DataSet
              
                sql = "Select * from sections "
               
                sql += " Select * from classes"
              
                
                
            
                      
                DS = SQLExec.Cursor(sql)
                
                
            %>

 <%  If DS.Tables(0).Rows.Count > 0 Then
                            For i = 0 To DS.Tables(0).Rows.Count - 1
                    %>

                    <li><a href="#"><%=DS.Tables(0).Rows(i)("sections")%></a>
                        <ul>
                            <%  If DS.Tables(1).Rows.Count > 0 Then

                                    For i1 = 0 To DS.Tables(1).Rows.Count - 1
                                        If (DS.Tables(0).Rows(i)("id") = DS.Tables(1).Rows(i1)("sectionId")) Then



                            %>

                            <li><a href="#"><%=DS.Tables(1).Rows(i1)("class")%></a></li>
                            <% End If
                                    Next
                                End If%>
                        </ul>

                    </li>
                    <% 
                                       Next
                                   End If%>

It is throwing an exception at this statement

If (DS.Tables(0).Rows(i)("id") = DS.Tables(1).Rows(i1)("sectionId")) Then

This is the error

Operator '=' is not defined for type 'Integer' and type 'DBNull'.

can please someone explain to me what is going on and how can I fix the problem

Thank you in advance

Answer 1

User1578460427 posted

lolo512

throwing an exception at this statement

If (DS.Tables(0).Rows(i)("id") = DS.Tables(1).Rows(i1)("sectionId")) Then

This is the error

Operator '=' is not defined for type 'Integer' and type 'DBNull'.

You need to check that each item in the If statement are not null using the IsDBNull function, then you can proceed to check whether both rows contain the the same id.

See solution at: Operator '=' is not defined for type 'DBNull' and type 'Integer'

Answer 2

User-1716253493 posted

Try this

If Convert.ToInt32(DS.Tables(0).Rows(i)("id")) = Convert.ToInt32(DS.Tables(1).Rows(i1)("sectionId")) Then

Answer 3

User-986267747 posted

Hi lolo512,

Operator '=' is not defined for type 'Integer' and type 'DBNull'.

can please someone explain to me what is going on and how can I fix the problem

According to your description, the problem is that the value you are trying to compare is DBnull, so you need to convert these value so that we could compare it with ohters form database. As eThunder say, you could use IsDBNull to solve your problem, i suggest that you could create a function and Pass the data in the database to the function so you can get the value you want to get.

 Private Function convertInteger(intInteger As Object) As Integer

        If IsDBNull(intInteger) Then
            Return 0
        End If

        Return intInteger

    End Function

If (convertInteger(DS.Tables(0).Rows(i)("id"))= convertInteger(DS.Tables(1).Rows(i1)("sectionId"))) Then

I hope it's helpful to you.

Best Regards,

Klein zhang