C＃数据导出到Excel-错误

Question

C# data export to excel - error

Hi all, hope in your help.

I am creating a C# 2010 Web application.

I have researched and test this and this should work...but I get an error and I can't get past this problem...my code below.

I would greatly appreciate any help you can give me in working this problem

CS0161: '_Default.GetData(System.Data.Odbc.OdbcCommand)': not all code paths return a value

private DataTable GetData(OdbcCommand cmd)
{
    DataTable dt = new DataTable();
    OdbcDataAdapter sda = new OdbcDataAdapter();

    cmd.CommandType = CommandType.Text;
    cmd.Connection = con;

    try
    {
        con.Open();
        sda.SelectCommand = cmd;
        sda.Fill(dt);

        if (dt.Rows.Count > 0)
        {
            return dt;
        }
        else
        {
            string strScript = "<script>" + "alert('Not found!.');";
            strScript += "window.location='default.aspx';";
            strScript += "</script>";
            Page.ClientScript.RegisterStartupScript(this.GetType(), "Startup", strScript);
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        con.Close();
        sda.Dispose();
        con.Dispose();
    }
}

Answer 1

Well, the compiler already told you what your problem is. You only return the DataTable if certain requirements are met. However a non-void method most return something in all possible code paths.

Answer 2

只需在结束括号之前添加

return dt;

Answer 3

The if clause checking for rows in the data table excludes the rest of the method from returning the signature the method dictates to be returned. You most likely want to get rid of the if/else clause and just return the data table regardless of the row count. Your code calling the method should be doing the checking for row count and rendering the alert. I would also highly recommend using StringBuilder when concatenating strings like that... Or since the string seems to be static text, use it as such with a constant.