Checking if an object is null in C#

in C# > 7 use if (obj is null)

For not null use:
   C# 7-8:  if (obj is object)
   C# 9-:    if (obj is not null)

These will ignore any == or != defined by the object (unless of course you want to use them for null checks)

[Edited to reflect hint by @kelton52]

Simplest way is to do object.ReferenceEquals(null, data)

Since (null==data) is NOT guaranteed to work:

class Nully
{
    public static bool operator ==(Nully n, object o)
    {
        Console.WriteLine("Comparing '" + n + "' with '" + o + "'");
        return true;
    }
    public static bool operator !=(Nully n, object o) { return !(n==o); }
}
void Main()
{
    var data = new Nully();
    Console.WriteLine(null == data);
    Console.WriteLine(object.ReferenceEquals(null, data));
}

Produces:

Comparing '' with 'Nully'

True

False

As of C# 9 you can do

if (obj is null) { ... }

For not null use

if (obj is not null) { ... }

If you need to override this behaviour use == and != accordingly.

As of C# 8 you can use the 'empty' property pattern (with pattern matching) to ensure an object is not null:

if (obj is { })
{
    // 'obj' is not null here
}

This approach means "if the object references an instance of something" (i.e. it's not null).

You can think of this as the opposite of: if (obj is null).... which will return true when the object does not reference an instance of something.

For more info on patterns in C# 8.0 read here.

With c#9 (2020) you can now check a parameter is null with this code:

if (name is null) { }

if (name is not null) { }

You can have more information here

Whenever you are creating objects of class you have to check the whether the object is null or not using the below code.

Example: object1 is object of class

void myFunction(object1)
{
  if(object1!=null)
  {
     object1.value1 //If we miss the null check then here we get the Null Reference exception
  }
}

I just followed a method that we would usually follow in java script. To convert object to string and then check whether they are null.

var obj = new Object();
var objStr = obj.ToString();
if (!string.IsNullOrEmpty(objStr)){
  // code as per your needs
}

I did more simple (positive way) and it seems to work well.

Since any kind of "object" is at least an object

    if (MyObj is Object)
    {
            //Do something .... for example:  
            if (MyObj is Button)
                MyObj.Enabled = true;
    }

You can try like below

public List<Object> dataList;
public  bool AddData(ref Object data)
bool success = false;
try
{
    if (data != null)
    {
       dataList.Add(data);
       success = doOtherStuff(data);
    }
}
catch (Exception e)
{
    throw new Exception(e.ToString());
}
return success;

}

Here are some extensions I use:

/// <summary>
/// Extensions to the object class
/// </summary>
public static class ObjectExtensions
{
    /// <summary>
    /// True if the object is null, else false
    /// </summary>
    public static bool IsNull(this object input) => input is null;

    /// <summary>
    /// False if the object is null, else true
    /// </summary>
    public static bool NotNull(this object input) => !IsNull(input);
}

There is a one-liner in .NET 6

ExampleMethod(null);

void ExampleMethod(object param)
{
    ArgumentNullException.ThrowIfNull(param);
    // Do something
}

public bool IsVisible(object ClaimCount)
    {
        bool flag = true;
        #region || HIDE COLUMNS ON CONDITION BASIS
        if (!String.IsNullOrEmpty(Convert.ToString(ClaimCount)))
        {
            Int32 ClaimCnt = Convert.ToInt32(ClaimCount);
            if (ClaimCnt == 1)
            {
                flag = false;
            }
        }
        #endregion
        return flag;
    }