how to check if a datareader is null or empty

Question

I have a datareader that return a lsit of records from a sql server database  I have a field in the database called  quot Additional quot   This field is 50  of the time empty or null  I am trying to write code that checks if this field isnull  The logic behind this is  If the field  quot Additional quot  contains text then display the info otherwise hide the field  I have tried  if  myReader  quot Additional quot      null        ltlAdditional Text    quot contains data quot     else        ltlAdditional Text    quot is null quot      The above code gives me this error  Exception Details  System IndexOutOfRangeException  Additional Any help would be greatly appreciated     See Also   Check for column name in a SqlDataReader object

User · Answer

I haven t used DataReaders for 3  years  so I wanted to confirm my memory and found this   Anyway  for anyone who happens upon this post like I did and wants a method to test IsDBNull using the column name instead of ordinal number  and you are using VS 2008    amp   NET 3 5 I think   you can write an extension method so that you can pass the column name in   public static class DataReaderExtensions       public static bool IsDBNull  this IDataReader dataReader  string columnName                 return dataReader columnName     DBNull Value            Kevin

User · Answer

if  myReader HasRows    The key Word is    HasRows           ltlAdditional Text    Contains data       else            ltlAdditional Text    Is null Or Empty

User · Answer

if  myReader  Additional      DBNull Value        ltlAdditional Text    contains data     else        ltlAdditional Text    is null

User · Answer

First of all  you probably want to check for a DBNull not a regular Null   Or you could look at the IsDBNull method

User · Answer

I also experiencing this kind of problem but mine  i m using DbDataReader as my generic reader  for SQL  Oracle  OleDb  etc    If using DataTable  DataTable has this method   DataTable dt   new DataTable    dt Rows 0  Table Columns Contains  SampleColumn      using this I can determine if that column is existing in the result set that my query has  I m also looking if DbDataReader has this capability

User · Answer

This  Example   objCar StrDescription    objSqlDataReader  fieldDescription   GetType      typeof DBNull      String objSqlDataReader  fieldDescription

User · Answer

In addition to the suggestions given  you can do this directly from your query like this -  SELECT ISNULL  Additional   -1  AS  Additional    This way you can write the condition to check whether the field value is  lt  0 or    0

User · Answer

AMG - Sorry all  was having a blond moment  The field  Additional  was added to the database after I had initially designed the database   I updated all my code to use this new field  however I forgot to update the actual datareader code that was making the call to select the database fields  therefore it wasn t calling  Additional

User · Answer

Joe Philllips  SQlDataReader IsDBNull int index  requires the ordinal number of the column  Is there a way to check for nulls using Column Name  and not it s Ordinal Number

User · Answer

This is the correct and tested solution  if  myReader Read           ltlAdditional Text    Contains data     else          ltlAdditional Text    Is null

User · Answer

Try this simpler equivalent syntax   ltlAdditional Text    myReader  Additional      DBNull Value     is null     contains data

User · Answer

I also use OleDbDataReader IsDBNull    if   myReader IsDBNull colNum      retrievedValue         else   retrievedValue   myReader GetString colNum

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