There is a null reference exception to merge two data table

Question

I'm going to call data from the DAL, send it to the BLL, and I'll give it to XtraReport. The scenario is as follows: In the DAL:

public static List<t_Products> GetAllProductList()
{
            try
            {
                return objContext.t_Products.OrderBy(c => c.f_ProName).ToList();
            }
......
}

in the BLL:

public static List<t_Products> GetAllProductList()
{
           return DAL.DALProducts.GetAllProductList();
       }

in the UI:

List<t_Products> ProductList = BLLProducts.GetAllProductList();
 var queryProduct=ProductList.Where(c => c.f_ProTypeID == 1)
                .Select(current=>new {current.f_ProductID,current.f_ProCode,current.f_P  roName,current.f_ProWeight,current.f_ProTypeID});
//create datatable from linq query
productDataTable =Utilities.IEnumerableToDataTable.LINQToDataTable(  queryProduct);

private void simpleButton1_Click(object sender, EventArgs e)
        {
            if (productDT.Rows.Count > 0)
            {
//sending datatable to Xtrareport
                Reports.XtraReports.ProductsAndBOM x = new Reports.XtraReports.ProductsAndBOM(productDT);
                x.Report();
            }
            else
....        }

Finally, I put in a XtraReport named ProductAndBOM, I have a DataSet called mahshamDataSet, in which there is a data table called t_Product. I've put the fields in this table on the report.I put the DataTable sent to the report, using the Merge command in the t_Product data table:

public partial class ProductsAndBOM : DevExpress.XtraReports.UI.XtraReport
    {
        public ProductsAndBOM()
        {
            InitializeComponent();
        }
        System.Data.DataTable requiredRawMaterilSource;
        System.Data.DataTable productsSource;
        public ProductsAndBOM(System.Data.DataTable products)
        {
            productsSource = products;
        }
        new public void Report()
        {
            mahshamDataSet1.t_Products.Merge(productsSource);
            ProductsAndBOM productBOMXtraReport = new ProductsAndBOM();
            ReportPrintTool printTool = new ReportPrintTool(productBOMXtraReport);
            UserLookAndFeel lookAndFeel = new UserLookAndFeel(this);
            lookAndFeel.UseDefaultLookAndFeel = false;
            lookAndFeel.SkinName = "Office 2016 Colorful";
            printTool.ShowRibbonPreview(lookAndFeel);
        }
    }

Unfortunately, when I merge the data table sent into the report with the mahshamDataSet1.t_Products table, I get the following error: An unhandled exception of type 'System.NullReferenceException' occurred in Mahsham.UI.exe Additional information: Object reference not set to an instance of an object.

Thanks, friends. Check the codes. See what I should do to avoid this error, and is this process correct, you think?. Thankful

Piroozman · Answer 1 · 2019-07-08T08:44:40.540

I got my problems:

public partial class ProductsAndBOM : DevExpress.XtraReports.UI.XtraReport
    {
        public ProductsAndBOM(System.Data.DataTable products)
        {
            InitializeComponent();
            productsSource = products;
        }
        //System.Data.DataTable requiredRawMaterilSource;
        System.Data.DataTable productsSource;

        public ProductsAndBOM()
        {

        }

        new public void Report()
        {
            //mahshamDataSet1 = new Data.MahshamDataSet();

           // ProductsAndBOM productBOMXtraReport = new ProductsAndBOM();
            mahshamDataSet1.t_Products.Merge(productsSource);
            ReportPrintTool printTool = new ReportPrintTool(this);
            UserLookAndFeel lookAndFeel = new UserLookAndFeel(this);
            lookAndFeel.UseDefaultLookAndFeel = false;
            lookAndFeel.SkinName = "Office 2016 Colorful";
            printTool.ShowRibbonPreview(lookAndFeel);
        }

    }

Before any initialization I tried to fill data table. Thankful.

There is a null reference exception to merge two data table

1 Answers1