C equivalent of the IsNull function in SQL Server

Question

In SQL Server you can use the IsNull   function to check if a value is null  and if it is  return another value  Now I am wondering if there is anything similar in C    For example  I want to do something like   myNewValue   IsNull myValue  new MyValue       instead of   if  myValue    null    myValue   new MyValue    myNewValue   myValue    Thanks

User · Accepted Answer

It s called the null coalescing      operator   myNewValue   myValue    new MyValue

User · Answer

For working with DB Nulls  I created a bunch for my VB applications  I call them Cxxx2 as they are similar to VB s built-in Cxxx functions   You can see them in my CLR Extensions project  http   www codeplex com ClrExtensions SourceControl FileView aspx itemId 363867 amp changeSetId 17967

User · Answer

Sadly  there s no equivalent to the null coalescing operator that works with DBNull  for that  you need to use the ternary operator   newValue    oldValue is DBNull    null   oldValue

User · Answer

You Write Two Function        When Expression is Number     public static double  isNull double  Expression  double  Value                if  Expression   null                        return Value                    else                       return Expression                          When Expression is string  Can not send Null value in string Expression     public static string isEmpty string Expression  string Value                if  Expression                              return Value                    else                       return Expression                    They Work Very Well

User · Answer

Use below methods            lt summary gt          Returns replacement value if expression is null          lt  summary gt           lt param name  expression  gt  lt  param gt           lt param name  replacement  gt  lt  param gt           lt returns gt  lt  returns gt      public static long  IsNull long  expression  long  replacement                if  expression HasValue              return expression          else             return replacement                  lt summary gt          Returns replacement value if expression is null          lt  summary gt           lt param name  expression  gt  lt  param gt           lt param name  replacement  gt  lt  param gt           lt returns gt  lt  returns gt      public static string IsNull string expression  string replacement                if  string IsNullOrWhiteSpace expression               return replacement          else             return expression

User · Answer

public static T IsNull lt T gt  this T DefaultValue  T InsteadValue                 object obj  kk            if  object  DefaultValue    DBNull Value                        obj   null                     if  obj  null    DefaultValue  null    DefaultValue ToString                              return InsteadValue                    else                       return DefaultValue                      This method can work with DBNull and null value  This method is question s answer

User · Answer

I ve been using the following extension method on my DataRow types       public static string ColumnIsNull this System Data DataRow row  string colName  string defaultValue                     string val   defaultValue          if  row Table Columns Contains colName                         if  row colName     DBNull Value                                val   row colName   ToString                                    return val          usage   MyControl Text   MyDataTable Rows 0  ColumnIsNull  MyColumn    MyOtherControl Text   MyDataTable Rows 0  ColumnIsNull  AnotherCol    Doh  I m null      I m checking for the existence of the column first because if none of query results has a non-null value for that column  the DataTable object won t even provide that column

User · Answer

This is meant half as a joke  since the question is kinda silly   public static bool IsNull  this System Object o       return  o    null       This is an extension method  however it extends System Object  so every object you use now has an IsNull   method   Then you can save tons of code by doing   if  foo IsNull      instead of the super lame   if  foo    null

User · Answer

Use the Equals method   object value2   null  Console WriteLine object Equals value2 null

User · Answer

public static T isNull lt T gt  this T v1  T defaultValue        return v1    null   defaultValue   v1     myValue isNull new MyValue

[c#] C# equivalent of the IsNull() function in SQL Server

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