Error: “The call is ambiguous between the following methods or properties”?

问题

When I run my project,the following error message is displayed:

The call is ambiguous between the following methods or properties: 'Microsoft.Reporting.WinForms.ReportDataSource.ReportDataSource(string, System.Collections.IEnumerable)' and 'Microsoft.Reporting.WinForms.ReportDataSource.ReportDataSource(string, System.Data.DataTable).

Why?

firstReportDBDataContext dc = new firstReportDBDataContext();
    private void Form1_Load(object sender, EventArgs e)
    {
        dsFirstReport.dtLoaiHangDataTable dt = new dsFirstReport.dtLoaiHangDataTable();
        var query = from a in dc.tblLoaiHangHoas
                    select a;
        foreach (tblLoaiHangHoa a in query)
        {
            dt.Rows.Add(a.MaLoai, a.TenLoai);
        }
         this.reportViewer1.LocalReport.DataSources.Add(new ReportDataSource("dsFirstReport_DataSet1",dt));
        this.reportViewer1.RefreshReport();

    }

回答1:

From the error message, it's clear that the type dsFirstReport.dtLoaiHangDataTable inherits the DataTable type and implements IEnumerable.

You can resolve the ambiguity for the compiler by casting the parameter to one or the other. E.g.:

reportViewer1.LocalReport.DataSources.Add(
    new ReportDataSource("dsFirstReport_DataSet1", (IEnumerable)dt));

来源：https://stackoverflow.com/questions/26931794/error-the-call-is-ambiguous-between-the-following-methods-or-properties