What is the proper way to check for null values?

Question

I love the null-coalescing operator because it makes it easy to assign a default value for nullable types.

 int y = x ?? -1;

That\'s great,

Answer 1

We use a method called NullOr.

Usage

// Call ToString() if it’s not null, otherwise return null
var str = myObj.NullOr(obj => obj.ToString());

// Supply default value for when it’s null
var str = myObj.NullOr(obj => obj.ToString()) ?? "none";

// Works with nullable return values, too —
// this is properly typed as “int?” (nullable int)
// even if “Count” is just int
var count = myCollection.NullOr(coll => coll.Count);

// Works with nullable input types, too
int? unsure = 47;
var sure = unsure.NullOr(i => i.ToString());

Source

/// 
Provides a function delegate that accepts only value types as return types.
/// This type was introduced to make 
/// work without clashing with .
public delegate TResult FuncStruct(TInput input) where TResult : struct;

/// 
Provides a function delegate that accepts only reference types as return types.
/// This type was introduced to make 
/// work without clashing with .
public delegate TResult FuncClass(TInput input) where TResult : class;

/// 
Provides extension methods that apply to all types.
public static class ObjectExtensions
{
    /// 
Returns null if the input is null, otherwise the result of the specified lambda when applied to the input.
    /// Type of the input value.
    /// Type of the result from the lambda.
    /// Input value to check for null.
    /// Function to apply the input value to if it is not null.
    public static TResult NullOr(this TInput input, FuncClass lambda) where TResult : class
    {
        return input == null ? null : lambda(input);
    }

    /// 
Returns null if the input is null, otherwise the result of the specified lambda when applied to the input.
    /// Type of the input value.
    /// Type of the result from the lambda.
    /// Input value to check for null.
    /// Function to apply the input value to if it is not null.
    public static TResult? NullOr(this TInput input, Func lambda) where TResult : struct
    {
        return input == null ? null : lambda(input);
    }

    /// 
Returns null if the input is null, otherwise the result of the specified lambda when applied to the input.
    /// Type of the input value.
    /// Type of the result from the lambda.
    /// Input value to check for null.
    /// Function to apply the input value to if it is not null.
    public static TResult? NullOr(this TInput input, FuncStruct lambda) where TResult : struct
    {
        return input == null ? null : lambda(input).Nullable();
    }
}