c# - Datatable Comparison of - primary keys is not working -

i have written code block compares datatable scheme differences.

this code:

    private static void validateschema(datatable originaltbl, datatable othertbl)     {                     var primarykeydoesnotmatch = originaltbl.primarykey != othertbl.primarykey;         if(primarykeydoesnotmatch)         {             throw new argumentexception("primary key not match");         }          var primarykeydoesnotexist = originaltbl.primarykey == null;         if(primarykeydoesnotexist)         {             throw new argumentexception("primary key not exist");         }          var othertablehasadditionalcolumns = (from x in othertbl.columns.oftype<datacolumn>() !originaltbl.columns.oftype<datacolumn>().any(y => y.columnname == x.columnname) select x).any();         if (othertablehasadditionalcolumns)         {             throw new argumentexception("other table have additional columns.");         }          var columnsaremissinginothertable = (from x in originaltbl.columns.oftype<datacolumn>() !othertbl.columns.oftype<datacolumn>().any(y => y.columnname == x.columnname) select x).any();         if (columnsaremissinginothertable)         {             throw new argumentexception("other table not have columns.");         }          var columndatatypesdoesnotmatch = (from x in othertbl.columns.oftype<datacolumn>() originaltbl.columns.oftype<datacolumn>().any(y => x.datatype != y.datatype) select x).any();         if (columndatatypesdoesnotmatch)         {             throw new argumentexception("column's data type not match");         }      } 

i have unit test has been implemented test these scenarios.

the problem when test "columndatatypedoesnotmatch" or "columnsaremissinginothertable" runs till first if statement , tells me "primary key not match" do!

any idea why happens?

your appreciated

tanx in advance.

sure. primarykey can never equal 1 (well, unless it's same table, or both have null - although should still have 2 separate new datacolumn[0] arrays), because you're performing reference comparison, , on array boot.

instead, have check example based on names of columns involved (and depending on requirements, data types well):

bool compare(datacolumn[] primary, datacolumn[] secondary) {   if (primary.length != secondary.length) return false;   var names = new hashset<string>(secondary.select(col => col.columnname));    return primary.all(col => names.contains(col.columnname)); } 

you'll have expand required per requirements, example based on whether care case sensitivity etc.