EmptyIf condition in SQL Server

I was facing a situation where if a database table column is empty, I need to set value as null otherwise the value of the column.

As there is no inbuilt function that does this, so here is the custom code for this.

   SELECT (CASE WHEN AuthorInfo = ''
   THEN NULL
   ELSE AuthorInfo END) AS AI FROM MyCategories 

In this case, if AuthorInfo column is empty, its value will be set as NULL for AI column otherwise actual value of AuthorInfo will be set.

 CREATE TABLE #temp_table 
(
i INT,strvalue varchar(10)
)

  INSERT INTO #temp_table (i,strvalue) VALUES (1,' ');

  INSERT INTO #temp_table (i,strvalue) VALUES (2,NULL);

INSERT INTO #temp_table (i,strvalue) VALUES (3,'HELLO');

  SELECT i,CASE strvalue WHEN '' 
                  THEN NULL 
             ELSE strvalue END AS AI FROM #temp_table