Check given string is integer or not

Create FUNCTION [dbo].[CheckIsInt](@String nvarchar(255)) 
RETURNS bit
AS 
BEGIN   
Declare @Count int,@char nchar(1),@result bit
SET @Count=1
SET @result =0
While (@Count<=len(@String))
BEGIN
    Set @char =substring(@String,@Count,1)
    if(charindex(@char,'0123456789')=0)
        return 0
    else
        SET @result=1   
    SET    @Count =@Count + 1
END
return @result

END