Handling FileNotFound Exception - vb.net

Question

cn.Open()
Dim query As String
query = "INSERT INTO Documents(AdmissionNumber,FullName,LeavingCertificate,KCPEResultSlip,BirthCertificate,MedicalCertificate,ParentOrGuardianPhoto,ParentGuardianIDFront,ParentGuardianIDBack,AnyOtherDocument) VALUES('" & Tbx1.Text & "','" & Tbx2.Text & "', #LeavingCertificate,#KCPEResultSlip,#BirthCertificate,#MedicalCertificate,#ParentOrGuardianPhoto,#ParentGuardianIDFront,#ParentGuardianIDBack,#AnyOtherDocument)"
cmd = New SqlCommand(query, cn)
cmd.Parameters.Add(New SqlClient.SqlParameter("#LeavingCertificate", SqlDbType.Image)).Value = IO.File.ReadAllBytes(OpenFileDialog1.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("#KCPEResultSlip", SqlDbType.Image)).Value = IO.File.ReadAllBytes(OpenFileDialog2.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("#BirthCertificate", SqlDbType.Image)).Value = IO.File.ReadAllBytes(OpenFileDialog3.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("#MedicalCertificate", SqlDbType.Image)).Value = IO.File.ReadAllBytes(OpenFileDialog4.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("#ParentOrGuardianPhoto", SqlDbType.Image)).Value = IO.File.ReadAllBytes(OpenFileDialog5.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("#ParentGuardianIDFront", SqlDbType.Image)).Value = IO.File.ReadAllBytes(OpenFileDialog6.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("#ParentGuardianIDBack", SqlDbType.Image)).Value = IO.File.ReadAllBytes(OpenFileDialog7.FileName)
cmd.Parameters.Add(New SqlClient.SqlParameter("#AnyOtherDocument", SqlDbType.Image)).Value = IO.File.ReadAllBytes(OpenFileDialog8.FileName)
Reader = cmd.ExecuteReader
MsgBox("Students' Documents Added Successfully to The Regista.", MsgBoxStyle.Information + MsgBoxStyle.OkOnly)
Btn9_Click(sender, e)
End Sub
' Hi comrades. You see this code above? This item called (AnyOtherDocument) is optional. The user can either provide it or Not. But when not provided, am getting an Exception error. How do I handle this?

Answer 1

Just check with File.Exists. If there is no file then set the parameter to DbNull.Value otherwise read the file
Dim exists = File.Exists(OpenFileDialog8.FileName)
.....
cmd.Parameters.Add(New SqlClient.SqlParameter( _
"#AnyOtherDocument", SqlDbType.Image)).Value _
= If(exists, IO.File.ReadAllBytes(OpenFileDialog8.FileName), _
DBNull.Value)
By the way, you are using parameters for all of your image values, why don't you use them also for the two string values? The usefulness of parameters is not tied to the DataType of the value to pass. You use them for every value to avoid Sql Injection and parsing problems
query = "INSERT INTO Documents " & _
"(AdmissionNumber,FullName,LeavingCertificate,KCPEResultSlip," & _
"BirthCertificate,MedicalCertificate,ParentOrGuardianPhoto," & _
"ParentGuardianIDFront,ParentGuardianIDBack,AnyOtherDocument) " & _
"VALUES(#admnum, #fullname, #LeavingCertificate,#KCPEResultSlip, " & _
"#BirthCertificate,#MedicalCertificate,#ParentOrGuardianPhoto," & _
"#ParentGuardianIDFront,#ParentGuardianIDBack,#AnyOtherDocument)"
cmd = New SqlCommand(query, cn)
cmd.Parameters.Add("#admnum", SqlDbType.NVarChar).Value = Tbx1.Text
cmd.Parameters.Add("#fullname", SqlDbType.NVarChar).Value = Tbx2.Text
cmd.Parameters.Add("#LeavingCertificate", SqlDbType.Image).Value = IO.File.ReadAllBytes(OpenFileDialog1.FileName)
.... and so on with all the other parameters ....