死ねばいいのに

FormHoge.vb

Private Sub Button1_Click(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles Button1.Click
  ' ...
  ' いろいろ処理

  Dim dataTable As DataTable = getDbData("hoge")

  ' ...
  ' いろいろ処理
End Sub

Private Sub Button2_Click(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles Button2.Click
  ' ...
  ' いろいろ処理

  Dim htPrm As New Hashtable
  htPrm.Add("@are", "are")
  htPrm.Add("@sore", "sore")
  Dim dataTable As DataTable = getDbData("fuga", htPrm)

  ' ...
  ' いろいろ処理
End Sub

Private Sub Button3_Click(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles Button3.Click
  ' ...
  ' いろいろ処理

  Dim htPrm As New Hashtable
  htPrm.Add("@are", "are")
  htPrm.Add("@kore", "kore")
  Dim htPrc As New Hashtable
  htPrc.Add("#where#", "are = @are AND kore = @kore")
  Dim dataTable As DataTable = getDbData("hage", htPrm, htPrc)

  ' ...
  ' いろいろ処理
End Sub

HogeClass.vb

Public Function getDbData(ByVal mode As String, Optional ByVal prm As Hashtable = Nothing, Optional ByVal prc As Hashtable = Nothing) As Object
    Dim sqlCommand as New SqlCommand
    Dim databaseHelper as DatabaseHelperClass   ' DBアクセス用のHelperクラス
    Dim dataTable As DataTable

    Dim sql As String = setSql(mode)
    If prc IsNot Nothing Then
        For Each key As String In prc.Keys
            sql = sql.Replace(key, prc(key))
        Next
    End If

    If prm IsNot Nothing Then
        For Each key As String In prm.Keys
            If key.IndexOf("@") = 0 Then
                sqlCommand.Parameters.AddWithValue(key, prm(key))
            End If
        Next
    End If

    Try
        databaseHelper.open(true)
        sqlCommand.Connection = databaseHelper.gConnection      ' ←DBのHelperクラスのPublicなフィールドに直でアクセス
        
        ' ...
        ' DBからデータ取得処理をゴニョゴニョ

        Return dataTable
    Catch ex As Exception
        Throw
    Finally
        databaseHelper.open(false)
    End Try

End Function

Private Function setSql(ByVal mode As String) As String
    Dim sql as New StringBuilder()
    With sql
        Select Case mode
            Case "hoge"
                .Append("SELECT")
                .Append("...")
                .Append("FROM ...")
            Case "fuga"
                .Append("SELECT")
                .Append("...")
                .Append("FROM ...")
                .Append("WHERE")
                .Append(" are = @are")
                .Append(" AND sore = @sore")
            Case "hage"
                .Append("SELECT")
                .Append("...")
                .Append("FROM ...")
                .Append("WHERE")
                .Append("#where#")
        End Select
    End With
    
    Return sql.toString()
End Function