CODEWITHSUNDEEP
c#string
syzygy78
syzygy78

Reputation: 145

Best practices before doing string manipulation in C#

Is there a recommended best practice for checking for NULL and empty (anything else?) before doing string manipulations, in C#? Specifically, I needed to call Replace and Trim on a string, but find that doing that on a NULL string throws. So is there a better format than the following?

tmp = (tmp == null) ? null : tmp.Replace("TOKEN", "").Trim();

Upvotes: 2

Views: 196

Answers (1)

Dai
Dai

Reputation: 155250

Use String.IsNullOrWhitespace in .NET 4.0 or later, or String.IsNullOrEmpty in .NET 3.x.

String temp = ...
if( !String.IsNullOrWhitespace( temp ) ) {
    temp = temp.Replace("TOKEN", "").Trim();
}

C# 6.0 adds the ?. operator, which is "null-safe", it just returns null and skips the rest of the navigation expression:

String temp = ...
temp = temp?.Replace("TOKEN", "").Trim();

As I remarked in my comment, if you're accessing a database using ADO.NET (DataSet, DataTable, IDataReader, etc) then you should check for DBNull which is used to indicate SQL NULL values, which are distinct from null in C#:

using( IDataReader rdr = command.ExecuteReader() ) {

    while( rdr.Read() ) {

        String value = rdr.IsDBNull( someColumnIndex ) ? null : rdr.GetString( someColumnIndex );
    }
}

Or:

DataTable table = ...
foreach( DataRow row in table.Rows ) {
    if( row["someColumn"] != DBNull.Value ) {
        String value = (String)row["someColumn"];
        // do stuff
    }
}

Upvotes: 8

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