Check If Record Is New Data

Posted on 2004-10-14
Last Modified: 2011-09-20
How do I check to see if new data entered into a bound textbox already exists in the table?
If it doesn’t then I need to fill some fields
However if it already exists I need to check if the text in another textbox matches a field an the current record, if it does then I need to fill some different fields

Question by:daverichardson
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LVL 28

Expert Comment

ID: 12310960
If DS.Tables("MyTable").Rows.Contains(me.textbox1.text) Then
    'Dont save
End If

Author Comment

ID: 12310995
i get an error
Input string was not in a correct format
LVL 28

Expert Comment

ID: 12311044
CHek the datatype. If you are looking for number do the cast.
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Author Comment

ID: 12311092
there are various columns in the table with various datatypes, but its only one column i need to search


Author Comment

ID: 12311098
can i specify the comumn?
LVL 28

Expert Comment

ID: 12311264
This code works for the primary key column. I f you want to check if this value exist the col must be primary key.
If it is not a case you have to create datareader for thsi column and then and loop through it
LVL 28

Expert Comment

ID: 12311307
Another approach would be to create unique field for this column and then put try catch block when you saving a record.
Let me know if you need help wiht unique field

Author Comment

ID: 12311321
could you point me in the right dirrection on how to do this
LVL 28

Accepted Solution

iboutchkine earned 125 total points
ID: 12311469
Here is an example how to create datatable with unique filelds

Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "
#End Region

    Private m_DataSet As DataSet
    Private m_dtPeople As DataTable

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ' Build the DataSet.
        m_DataSet = New DataSet()

        ' Build the People table.
        m_dtPeople = New DataTable("People")
        m_dtPeople.Columns.Add("LastName", GetType(String))
        m_dtPeople.Columns.Add("FirstName", GetType(String))
        m_dtPeople.Columns.Add("Notes", GetType(String))

        ' Make the UniqueConstraint on LastName
        ' and FirstName.
        Dim data_columns(1) As DataColumn
        Dim unique_constraint As UniqueConstraint

        data_columns(0) = m_dtPeople.Columns("LastName")
        data_columns(1) = m_dtPeople.Columns("FirstName")
        unique_constraint = New UniqueConstraint(data_columns)

        ' Populate the People table.
        Dim people_data(2) As String
        people_data(0) = "Abercrombe"
        people_data(1) = "Alice"
        people_data(2) = ""

        people_data(0) = "Bouf"
        people_data(1) = "Brian"
        people_data(2) = ""

        people_data(0) = "Carnivale"
        people_data(1) = "Cynthia"
        people_data(2) = "Phone: 987-654-3210"

        ' Attach the DataGrid to the DataTable.
        dgPeople.DataSource = m_dtPeople
    End Sub
End Class

Now if you try to add duplicate field you will get an exception. Put your save record to the try-catch block and catch this exception

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