null value return from database how to handle it in asp.net vb

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Here i use code like this

C#

Dim qry="select max(ID) from tbl_deal where officeid='" & ddl1.SelectedValue.Trim & "'"
dun cmd1 as sqlCommand=New SqlCommand(qry,conn)
conn.open()
dim read As SqlDataReader=cmd1.ExecuteReader()
read.Read()
Dim a=0
if(read.HasValue) Then
a=read(0)
endif
a=a+1

but this code given error in nullvalue its not 1.Thanks
Regards,
Umesh Daiya

Posted 10-Jul-13 20:05pm

UDTWS

Updated 10-Jul-13 20:24pm

Thanks7872

v2

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Maciej Los · Answer 1 · 2013-07-11T00:19:00

Solution 4

Please, use below query:

SQL

select COALESCE(max(ID),0) from tbl_deal where officeid=@officeid

That resolves your problem with DbNull.

Posted 11-Jul-13 0:19am

Maciej Los

Dholakiya Ankit · Answer 2 · 2013-07-10T20:07:00

Solution 1

give convert.tostring to read(0) if its null then 0 and if its not null then your function a=a+1 and convert read to int if not null ............ convert.tostring can handle null values also it will not throw error

Posted 10-Jul-13 20:07pm

Dholakiya Ankit

Updated 10-Jul-13 20:08pm

v2

Comments

UDTWS 11-Jul-13 5:18am

Thanks for reply, i try this code to convert into string in if but error msg Conversion from string "" to type 'Bolean' is not valid

Dholakiya Ankit 11-Jul-13 5:41am

try like this if (convert.tostring( read.HasValue)=="")

Krishna KV · Answer 3 · 2013-07-10T21:20:00

Solution 2

VB

If not read(0)= DBNull.Value Then
a=read(0)
end if

Posted 10-Jul-13 21:20pm

Krishna KV

Comments

UDTWS 11-Jul-13 5:20am

Thanks for reply,
but i got an error msg like this DBNull is a type and cannot be used as an expression

UDTWS · Answer 4 · 2013-07-11T00:13:00

Solution 3

VB

if Convert.ToString(read(0))<>"" Then
a=read(0)
else
a=a+1
Endif

Posted 11-Jul-13 0:13am

UDTWS