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Check column exists in SqlReader using Linq

Posted on 2011-10-06
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Last Modified: 2012-05-12
The only way to check if a column exists in a SqlDataReader is by looping through the columns

http://stackoverflow.com/questions/373230/check-for-column-name-in-a-sqldatareader-object

can anyone give me some linq to do this so I can put the check in a single statement?
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Question by:purplesoup
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5 Comments
 
LVL 15

Expert Comment

by:Navneet
ID: 36923705
HI!

You can try this as well

if (reader.GetSchemaTable().Columns["COLUMNNAME"] != null)


Thanks!

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Author Comment

by:purplesoup
ID: 36923783
This isn't quite right is it - the SchemaTable returned is a table about the resultset, and the columns are ColumnName, ColumnOrdinal, ColumnSize etc, so it will only tell me about the columns in the schema table, not the columns in the resultset.

If for example I want to know if a column called "Sequence" is in my result set,

if (reader.GetSchemaTable().Columns["Sequence"] != null)

won't do it.
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LVL 15

Accepted Solution

by:
Navneet earned 2000 total points
ID: 36923841
Hi!

add this class
    static  class MyName
    {

        /// <summary>
        /// Checks if a column exists in the DataReader
        /// </summary>
        /// <param name="dr">DataReader</param>
        /// <param name="ColumnName">Name of the column to find</param>
        /// <returns>Returns true if the column exists in the DataReader, else returns false</returns>
        public static Boolean ColumnExists(this IDataReader dr, String ColumnName)
        {
            for (Int32 i = 0; i < dr.FieldCount; i++)
                if (dr.GetName(i).Equals(ColumnName, StringComparison.OrdinalIgnoreCase))
                    return true;

            return false;
        }
    }

Open in new window


Adding above extension to IDataReader
check your sqlDataReader for Column like :

sqlDataReader.ColumnExists("Sequence");

Thanks!
0
 

Author Comment

by:purplesoup
ID: 36924611
That's pretty clever - I'll wait a little longer if you don't mind just to see if anyone comes up with anything as good...
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Author Closing Comment

by:purplesoup
ID: 37024356
Sorry - I didn't actually intend to wait quite so long..
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