C# Check if object exists before referencing -

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• what nullreferenceexception, , how fix it? 29 answers

i wondering if there's way check if object exists before referencing @ all. not check if null because isn't working either. using epplus package read excel files , when gets index not have value data in it, sends exception.

private datatable worksheettodatatable(string tablename) {     excelsheet = excelworkbook.worksheets[tablename];     datatable dt = new datatable();     try     {         int totalrows = excelsheet.dimension.end.row;         int totalcols = excelsheet.dimension.end.column;         (int j = 1; j <= totalcols; j++)         {              dt.columns.add();             (int = 1; <= totalrows; i++)             {                 if (j == 1)                 {                     dt.rows.add();                 }                 try                 {                     dt.rows[i - 1][j - 1] = excelsheet.cells[i, j].value.tostring();                     //dt.rows[i - 1][j - 1] = object.referenceequals(null, excelsheet.cells[i, j].value.tostring()) ? "" : excelsheet.cells[i, j].value.tostring();                 }                 catch                 {                     dt.rows[i - 1][j - 1] = "";                 }             }         }         return dt;     }     catch     {         messagebox.show("error: referenced excel table empty, or indexed improperly! check excel formatting.", "error");         return dt;     } } 

so can see i've tried checking if excelsheet.cells[i, j].value.tostring() null before , sends same exception caught in try/catch have above. have parse lot of cells , lot of them empty, adds lot of

exception thrown: 'system.nullreferenceexception' in bbsapp.exe

to output console. there way check if object exists before call object check if null without try/catch?

if(excelsheet.cells[i, j].value.tostring() != null) 

simply checking if null shown above sends same exception because not exist in first place.

try this:

if(excelsheet.cells[i, j].value != null) 

you're checking see value property null. null reference exception occurs because trying call method tostring() on null object.

alternatively, can use null access operator:

if(excelsheet.cells[i, j]?.value?.tostring() != null)