SQL to search for encrypted values not working - sql

Question

I am using a button to trigger a SELECT statement, and based off of the criteria the user enters in 2 text boxes (SearchFirstTxt, SearchLastTxt), I send the Text values of those text boxes through an encryption class to find their match
I return them in a SqlDataAdapter and use it to fill a DataTable. I then use DataGridView.DataSoruce = dt to add it to the DGV.
My question: If the user leaves both text boxes blank and clicks the "SearchBtn", it doesn't select all of the records. It actually only selects records with the same encrypted values.
Here is the code:
eFirst = clsEncrypt.EncryptData(SearchFirstTxt.Text.Trim.ToUpper)
eLast = clsEncrypt.EncryptData(SearchLastTxt.Text.Trim.ToUpper)
conn.Open()
cmd.Connection = conn
If SearchFirstTxt.Text = "" Then
cmd.CommandText = "Select * FROM Participant Where LAST_NM_TXT = '" & eLast & "' ; "
ElseIf SearchLastTxt.Text = "" Then
cmd.CommandText = "Select * FROM Participant WHERE FIRST_NM_TXT = '" & eFirst & "' ; "
Else
cmd.CommandText = "SELECT * FROM PARTICIPANT;"
End If
Dim adapter As New SqlDataAdapter(cmd)
adapter.Fill(dt)
DataGridView1.DataSource = dt
Try
For i As Integer = 0 To dt.Rows.Count - 1
dt.Rows(i)("FIRST_NM_TXT") = clsEncrypt.DecryptData(eFirst)
dt.Rows(i)("LAST_NM_TXT") = clsEncrypt.DecryptData(eLast)
Next
Catch ex As Exception
MessageBox.Show("Error")
Finally
conn.Close()
End Try
How can I select ALL of the records from the Participant dbo?
The result set looks like this if the text boxes are left blank:
Edit: I switched my code, and it retrieves ALL of the results, however, now I am having difficulty returning them. (They return as encrypted, but not decrypted)
Here are the changes:
If SearchFirstTxt.Text = "" And SearchLastTxt.Text = "" Then
cmd.CommandText = "SELECT * FROM PARTICIPANT;"
ElseIf SearchLastTxt.Text = "" Then
cmd.CommandText = "Select * FROM Participant WHERE FIRST_NM_TXT = '" & eFirst & "' ; "
ElseIf SearchFirstTxt.Text = "" Then
cmd.CommandText = "Select * FROM Participant Where LAST_NM_TXT = '" & eLast & "' ; "
End If

Answer 1

If I understand your requirements correctly, you need to add a check for the other search text when you try to search your encrypted data
If SearchFirstTxt.Text = "" AndAlso SearchLastTxt.Text <> "" Then
' Search the last only if you have a last and not a first'
cmd.CommandText = "Select * FROM Participant Where LAST_NM_TXT = #searchLast"
cmd.Parameters.AddWithValue("#searchLast", eLast)
ElseIf SearchLastTxt.Text = "" AndAlso SearchFirstTxt.Text <> "" Then
' Search the first only if you have a first and not a last'
cmd.CommandText = "Select * FROM Participant WHERE FIRST_NM_TXT = #searchFirst"
cmd.Parameters.AddWithValue("#searchFirst", eFirst)
ElseIf SearchFirstTxt.Text = "" AndAlso SearchLastText.Text = "" Then
' Both emtpy so search everything'
cmd.CommandText = "SELECT * FROM PARTICIPANT;"
Else
' Both filled so search exactly (not sure if this is needed)'
cmd.CommandText = "Select * FROM Participant " & _
"WHERE FIRST_NM_TXT = #searchFirst " & _
"OR LAST_NM_TXT = #searchLast"
cmd.Parameters.AddWithValue("#searchFirst", eFirst)
cmd.Parameters.AddWithValue("#searchLast", eLast)
End If
Dim adapter As New SqlDataAdapter(cmd)
adapter.Fill(dt)
Notice that I have removed your string concatenation and used a parameterized query. It is safer (avoids Sql Injection) and remove parsing problems (what if your encrypted text contains a single quote?)
Supposing then that you want to show the decrypted data you apply your deCryptData function to the values in the datatable, not to the same values used for the search (you already know the clear text)
Try
For i As Integer = 0 To dt.Rows.Count - 1
dt.Rows(i)("FIRST_NM_TXT") = clsEncrypt.DecryptData(dt.Rows(i)("FIRST_NM_TXT").ToString)
dt.Rows(i)("LAST_NM_TXT") = clsEncrypt.DecryptData(dt.Rows(i)("LAST_NM_TXT").ToString)
Next
Catch ex As Exception
MessageBox.Show("Error")
Finally
conn.Close()
End Try