Check if a table or field exists in a database

Introduction

These are two functions I wrote in VB.NET using ADO.NET to check and see if a table or a field exists in a database. It can work with MS Access, or SQL Server, or any other OLE database.

Background

Checking if a table or a field exists in an Access database should be a very simple task, but it can become very complicated with ADO.NET. With DAO or ADO in VB 6.0, this was an extremely easy task. Those who have used it will agree. So, I am posting these functions to help other programmers. Hopefully, it will help out some.

Using the code

Here are the functions:

''' <summary>
''' Checks to see if a table exists in Database or not.
''' </summary>
''' <param name="tblName">Table name to check</param>
''' <param name="cnnStr">Connection String to connect to</param>
''' <returns>Works with Access or SQL</returns>
''' <remarks></remarks>

Public Function DoesTableExist(ByVal tblName As String, ByVal cnnStr As String) As Boolean
    ' For Access Connection String,
    ' use "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" &
    ' accessFilePathAndName

    ' Open connection to the database
    Dim dbConn As New OleDbConnection(cnnStr)
    dbConn.Open()
    
    ' Specify restriction to get table definition schema
    ' For reference on GetSchema see:
    ' http://msdn2.microsoft.com/en-us/library/ms254934(VS.80).aspx

    Dim restrictions(3) As String
    restrictions(2) = tblName
    Dim dbTbl As DataTable = dbConn.GetSchema("Tables", restrictions)

    If dbTbl.Rows.Count = 0 Then
        'Table does not exist
        DoesTableExist = False
    Else
        'Table exists
        DoesTableExist = True
    End If

    dbTbl.Dispose()
    dbConn.Close()
    dbConn.Dispose()
End Function


''' <summary>
''' Checks to see if a field exists in table or not.
''' </summary>
''' <param name="tblName">Table name to check in</param>
''' <param name="fldName">Field name to check</param>
''' <param name="cnnStr">Connection String to connect to</param>
''' <returns></returns>
''' <remarks></remarks>
Public Function DoesFieldExist(ByVal tblName As String, _
                               ByVal fldName As String, _
                               ByVal cnnStr As String) As Boolean
    ' For Access Connection String,
    ' use "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" &
    ' accessFilePathAndName

    ' Open connection to the database
    Dim dbConn As New OleDbConnection(cnnStr)
    dbConn.Open()
    Dim dbTbl As New DataTable

    ' Get the table definition loaded in a table adapter
    Dim strSql As String = "Select TOP 1 * from " & tblName
    Dim dbAdapater As New OleDbDataAdapter(strSql, dbConn)
    dbAdapater.Fill(dbTbl)

    ' Get the index of the field name
    Dim i As Integer = dbTbl.Columns.IndexOf(fldName)

    If i = -1 Then
        'Field is missing
        DoesFieldExist = False
    Else
        'Field is there
        DoesFieldExist = True
    End If

    dbTbl.Dispose()
    dbConn.Close()
    dbConn.Dispose()
End Function

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)