Code:
this->treeView->BeginUpdate();

        this->treeView->Nodes->Add(gcnew TreeNode("Ime firme"));
        this->treeView->Nodes[0]->ImageIndex = 4;
        this->treeView->Nodes[0]->SelectedImageIndex = 4;
        this->treeView->Nodes[0]->Nodes->Add(gcnew TreeNode("Radnici"));
        this->treeView->Nodes[0]->Nodes[0]->ImageIndex = 0;
        this->treeView->Nodes[0]->Nodes[0]->SelectedImageIndex = 0;
        ArrayList^ arr = gcnew ArrayList;
        arr->Add("stanje");
        arr->Add("u/i");
        arr->Add("vrijeme");
        IEnumerator^ mEnum = arr->GetEnumerator();
        while (mEnum->MoveNext())
        {
            String^ tree = safe_cast<String^>(mEnum->Current);
            this->treeView->Nodes[0]->Nodes[0]->Nodes->Add(gcnew TreeNode(tree));
            this->treeView->Nodes[0]->Nodes[0]->Nodes[arr->IndexOf(mEnum->Current)]->ImageIndex = 1;
            this->treeView->Nodes[0]->Nodes[0]->Nodes[arr->IndexOf(mEnum->Current)]->SelectedImageIndex = 1;
        }
        this->treeView->Nodes[0]->Nodes->Add(gcnew TreeNode("Gosti"));
        this->treeView->Nodes[0]->Nodes[1]->ImageIndex = 2;
        this->treeView->Nodes[0]->Nodes[1]->SelectedImageIndex = 2;
        arr->Clear();
        arr->Add("stanje");
        arr->Add("evidencija");
        mEnum = arr->GetEnumerator();
        while (mEnum->MoveNext())
        {
            String^ tree = safe_cast<String^>(mEnum->Current);
            this->treeView->Nodes[0]->Nodes[1]->Nodes->Add(gcnew TreeNode(tree));
            this->treeView->Nodes[0]->Nodes[1]->Nodes[arr->IndexOf(mEnum->Current)]->ImageIndex = 1;
            this->treeView->Nodes[0]->Nodes[1]->Nodes[arr->IndexOf(mEnum->Current)]->SelectedImageIndex = 1;
        }
        arr->Clear();

        this->treeView->Nodes[0]->Nodes->Add(gcnew TreeNode("Organizacija"));
        this->treeView->Nodes[0]->Nodes[2]->ImageIndex = 3;
        this->treeView->Nodes[0]->Nodes[2]->SelectedImageIndex = 3;
        
        String^ command = "select * from sektor";
        SqlConnection^ connection = gcnew SqlConnection(connectionString);
        //dataAdapter = gcnew SqlDataAdapter();
        dataAdapter->SelectCommand = gcnew SqlCommand(command,connection);
        dataAdapter->Fill(m_ds->Tables["sektor"]);
        
        command = "select * from sekcija";
        dataAdapter->SelectCommand = gcnew SqlCommand(command,connection);
        dataAdapter->Fill(m_ds->Tables["sekcija"]);

        command = "select * from radnajedinica";
        dataAdapter->SelectCommand = gcnew SqlCommand(command,connection);
        dataAdapter->Fill(m_ds->Tables["radnajedinica"]);
        
        array<DataRow^>^ x_row = m_ds->Tables["sektor"]->Select();
        int i;
        for (i=0;i<x_row->Length;i++)
        {
             String^ tree = safe_cast<String^>(x_row[i]["opis"]);
             this->treeView->Nodes[0]->Nodes[2]->Nodes->Add(gcnew TreeNode(tree));
             this->treeView->Nodes[0]->Nodes[2]->Nodes[i]->ImageIndex = 3;
             this->treeView->Nodes[0]->Nodes[2]->Nodes[i]->SelectedImageIndex = 3;

             array<DataRow^>^ y_row = m_ds->Tables["sekcija"]->Select("sektor = '" +
                 x_row[i]["sifra"] +"'");
             int j;
             for (j=0;j<y_row->Length;j++)
             {
                 String^ tree = safe_cast<String^>(y_row[j]["opis"]);
                 this->treeView->Nodes[0]->Nodes[2]->Nodes[i]->Nodes->Add(gcnew TreeNode(tree));
                 this->treeView->Nodes[0]->Nodes[2]->Nodes[i]->Nodes[j]->ImageIndex = 3;
                 this->treeView->Nodes[0]->Nodes[2]->Nodes[i]->Nodes[j]->SelectedImageIndex = 3;
             
                 array<DataRow^>^ z_row = m_ds->Tables["radnajedinica"]->Select("sekcija = '" +
                     y_row[j]["sifra"] +"'");
                 int k;
                 for (k=0;k<z_row->Length;k++)
                 {
                      String^ tree = safe_cast<String^>(z_row[k]["sifra"]);
                      this->treeView->Nodes[0]->Nodes[2]->Nodes[i]->Nodes[j]->Nodes->Add(gcnew TreeNode(tree));
                      this->treeView->Nodes[0]->Nodes[2]->Nodes[i]->Nodes[j]->Nodes[k]->ImageIndex = 1;
                      this->treeView->Nodes[0]->Nodes[2]->Nodes[i]->Nodes[j]->Nodes[k]->SelectedImageIndex = 1;
                 }
                 delete []z_row;
             }
             delete []y_row;
        
        }
        delete []x_row;
        m_ds->Tables["radnajedinica"];
        m_ds->Tables["sektor"];
        m_ds->Tables["sekcija"];

    
        this->treeView->EndUpdate();
        this->treeView->Nodes[0]->Expand();
        this->treeView->Nodes[0]->Nodes[0]->Expand();