c# - Casting DBNull to boolean -

hello can't seems solve cast operation. error:

string not recognized valid boolean

for line

iskey = convert.toboolean(row["iskey"].tostring()); 

i'm using datareader table schema. iskey presently null everywhere in db. want true or false result.

tableschema = myreader.getschematable();       foreach (datarow row in tableschema.rows) {     string columnname = row["columnname"].tostring();     string columntype = row["datatypename"].tostring();                    bool iskey = convert.toboolean(row["iskey"].tostring()); 

first, use format getting values datarow:

string columnname = row.field<string>("columnname"); string columntype = row.field<string>("datatypename");  //this uses first , second variable call example 

this defines returning value , conversion you.

your problem have column bit (or @ least hope it's bit), allows nulls. means datatype in c# bool?. use this:

bool? iskey = row.field<bool?>("iskey"); 

---

your second question (in comments):

if bool? iskey return null how can convert false?

the easiest way use null-coalescing operator

bool iskey = row.field<bool?>("iskey") ?? false; 

this says: "give me first thing not null, either column value or "false".