Difference between var and default datatype is explained below:
|Introduced in C# 3.0||Introduced in C# 4.0|
|Statically typed – This means the type of variable declared is decided by the compiler at compile time.||Dynamically typed – This means the type of variable declared is decided by the compiler at runtime time.|
|Need to initialize at the time of declaration.
e.g., var str=”I am a string”;
Looking at the value assigned to the variable str, the compiler will treat the variable str as string.
|No need to initialize at the time of declaration.
e.g., dynamic str;
str=”I am a string”; //Works fine and compiles
str=2; //Works fine and compiles
|Errors are caught at compile time.
Since the compiler knows about the type and the methods and properties of the type at the compile time itself
|Errors are caught at runtime
Since the compiler comes to about the type and the methods and properties of the type at the run time.
|Visual Studio shows intellisense since the type of variable assigned is known to compiler.||Intellisense is not available since the type and its related methods and properties can be known at run time only|
|e.g., var obj1;
will throw a compile error since the variable is not initialized. The compiler needs that this variable should be initialized so that it can infer a type from the value.
|e.g., dynamic obj1;
|e.g. var obj1=1;
var obj1=” I am a string”;
will throw error since the compiler has already decided that the type of obj1 is System.Int32 when the value 1 was assigned to it. Now assigning a string value to it violates the type safety.
|e.g. dynamic obj1=1;
will compile and run
dynamic obj1=” I am a string”;
will compile and run since the compiler creates the type for obj1 as System.Int32 and then recreates the type as string when the value “I am a string” was assigned to it.
This code will work fine.