A function to convert null to string

Question

I want to create a function to convert any null value e g  from a database to an empty string  I know there are methods such as if value    null    value   String Empty but is there a way to pass null to a method e g   public string nullToString string  value        if value    null  return empty      return value     But I am not sure on the parameter syntax to do this    I tried the above but it says not a nullable type   Thanks in advance

User · Answer

According to the following MSDN page  you need the Convert ToString method string x   Convert ToString  object value

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1  string Format  You can use string Format which converts null to empty string  string nullstr   null  string  quotestring   string Format   0    nullstr   Console WriteLine quotestring    Output-      2 string interpolation  or you can use string interpolation  this feature is available in C  6 and later versions   InterpolatedExpression produces a result to be formatted  A string representation of the null result is String Empty    string nullstr   null   string  quotestring      nullstr     Console WriteLine quotestring    Output-

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Sometimes I just append an empty string to an object that might be null  object x   null  string y    x    quot  quot   ToString     This will never throw an exception and always return an empty string if null and doesn t require if then logic

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you can use      for example    y x       if x isn t null y x but if x is null y

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When you get a NULL value from a database  the value returned is DBNull Value on which case  you can simply call  ToString   and it will return     Example     reader  Column   ToString      Gets you    if the value returned is DBNull Value  If the scenario is not always a database  then I d go for an Extension method   public static class Extensions        public static string EmptyIfNull this object value                if  value    null              return             return value ToString              Usage    string someVar   null   someVar EmptyIfNull

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static string NullToString  object Value             Value ToString   allows for Value being DBNull  but will also convert int  double  etc      return Value    null        Value ToString            If this is not what you want then this form may suit you better  handles  Null  and DBNull otherwise tries a straight cast        which will throw if Value isn t actually a string object        return Value    null    Value    DBNull Value         string Value

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Its possible to make this even shorter with C  6   public string NullToString string Value        return value  ToString

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You can try this  public string ToString this object value           this will throw an exception if value is null     string val   Convert ToString  value            it can be a space      If  string IsNullOrEmpty val Trim              return string Empty           to avoid not all code paths return a value     return val

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You can just use the null coalesce operator   string result   value

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Convert ToString object  converts to string  If the object is null  Convert ToString converts it to an empty string    Calling  ToString   on an object with a null value throws a System NullReferenceException   EDIT   Two exceptions to the rules   1  ConvertToString string  on a null string will always return null   2  ToString Nullable lt T gt   on a null value will return       Code Sample      1  Objects   object obj   null     string valX1   obj ToString                 throws System NullReferenceException     string val1   Convert ToString obj        Console WriteLine val1            True Console WriteLine val1    null      False      2  Strings  String str   null    string valX2   str ToString          throws System NullReferenceException     string val2   Convert ToString str     Console WriteLine val2            False Console WriteLine val2    null      True                  3  Nullable types   long  num   null  string val3   num ToString        ok  no error  Console WriteLine num    null      True Console WriteLine val3             True Console WriteLine val3    null      False   val3   Convert ToString num      Console WriteLine num    null       True Console WriteLine val3             True Console WriteLine val3    null      False

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public string nullToString string value        return value    null  string Empty  value

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It is possible to use the       null conditional member access  with the       null-coalescing operator  like this   public string EmptyIfNull object value        return value  ToString      string Empty      This method can also be written as an extension method for an object   public static class ObjectExtensions       public static string EmptyIfNull this object value                return value  ToString      string Empty            And you can write same methods using       lambda operator    public string EmptyIfNull object value        gt  value  ToString      string Empty

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Its an old topic  but there is a  elegant  way to do that     static string NullToString  object Value                return Value   Value    string Empty

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public string ToString this string value                        if  value    null                                value   string Empty                                           else                               return value Trim

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You can use Convert ToString  object value   You need to cast your value to an object first  otherwise the conversion will result in a null   using System   public class Program       public static void Main                 string format        Convert ToString  0 -20      null   1 -5       empty   2 -5            object nullObject   null          string nullString   null           string convertedString   Convert ToString nullObject           Console WriteLine format   nullObject   convertedString    null  convertedString                  convertedString   Convert ToString nullString           Console WriteLine format   nullString   convertedString    null  convertedString                  convertedString   Convert ToString  object nullString           Console WriteLine format    object nullString   convertedString    null  convertedString                    Gives   Convert ToString nullObject               null  False      empty  True  Convert ToString nullString               null  True       empty  False Convert ToString  object nullString       null  False      empty  True   If you pass a System DBNull Value to Convert ToString   it will be converted to an empty string too

[c#] A function to convert null to string

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