Как разрешить ошибку C# " выражение небулевого типа, заданное в контексте, где ожидается условие, рядом '

error "An expression of non-boolean type specified in a context where a condition is expected, near '

public partial class ProductWiseReportViewer : Form
{
    SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=StockSF;Integrated Security=True");
    ReportDocument crypt = new ReportDocument();
    public ProductWiseReportViewer()
    {
        InitializeComponent();
    }

    public DateTime date1 { get; set; }

    public DateTime date2 { get; set; }

    public object prname { get; set; }

    private void crystalReportViewer1_Load(object sender, EventArgs e)
    {
        //this.reportViewer1.RefreshReport();
        SqlDataAdapter sda = new SqlDataAdapter("SELECT * FROM tblPurchase WHERE Pur_Date between '" + date1 + "'and '" + date2 + "'and'"+prname+"'",con);
        DataTable dt = new DataTable();
        DataSet dst = new DataSet();
        sda.Fill(dst, "tblPurchase");
        crypt.Load(@"F:\Project C#\StockSF\StockSF\RptPurchase.rpt");
        crypt.SetDataSource(dst);
        crystalReportViewer1.ReportSource = crypt;
    }
}