Set of processing functions for strings

The following string has a set of processing functions from Seaskyer
#region "set of processing functions for strings"

<summary>
Set of processing functions for strings
</summary>
public class Str
{
<summary>
Converts a Stream into a string
</summary>
<param name= "s" > Stream flow </param>
<returns> string </returns>
public static string convertstreamtostring (Stream s)
{
String strresult = "";
StreamReader sr = new StreamReader (s, Encoding.UTF8);

char[] Read = new char[256];

Read 256 charcters at a time.
int count = Sr. Read (read, 0, 256);

while (Count > 0)
{
Dump the 256 characters on a string and display the string onto the console.
String str = new string (read, 0, Count);
Strresult + + str;
Count = Sr. Read (read, 0, 256);
}


Releasing resources
Sr. Close ();

return strresult;
}

<summary>
Handles the passed parameter string to prevent an injection attack
</summary>
<param name= "str" > passed parameter string </param>
<returns> String </returns>
public static string Convertsql (String str)
{
str = str. Trim ();
str = str. Replace ("'", "" ");
str = str. Replace (";-", "");
str = str. Replace ("=", "");
str = str. Replace ("or", "");
str = str. Replace ("and", "");

return str;
}


<summary>
Format the output of the occupied space size
</summary>
<param name= "Size" > Size </param>
<returns> return String </returns>
public static string Formatnum (long size)
{
Decimal NUM;
String strresult;

if (Size > 1073741824)
{
NUM = (convert.todecimal (size)/Convert.todecimal (1073741824));
strresult = NUM. ToString ("N") + "M";
}
else if (Size > 1048576)
{
NUM = (convert.todecimal (size)/Convert.todecimal (1048576));
strresult = NUM. ToString ("N") + "M";
}
else if (Size > 1024)
{
NUM = (convert.todecimal (size)/convert.todecimal (1024));
strresult = NUM. ToString ("N") + "KB";
}
Else
{
strresult = size + "byte";
}

return strresult;
}

<summary>
To determine whether a string is a valid mailing address
</summary>
<param name= "Email" ></param>
<returns></returns>
public static bool IsValidEmail (string email)
{
return Regex.IsMatch (email, @ "^.+@") [a-za-z0-9-.] +. ([a-za-z]{2,3}| [0-9] {1,3}) (]?) $ " );
}

<summary>
Determines whether a string is a valid URL address
</summary>
<param name= "url" ></param>
<returns></returns>
public static bool Isvalidurl (string URL)
{
return Regex.IsMatch (URL, @ "^ (http|https|ftp)://[a-za-z0-9-.] +. [A-za-z] {2,3} (: [a-za-z0-9]*)?/? ([A-za-z0-9-._, '//+&%$#=~]) *[^.,) (s]$ ");
}

<summary>
that determines whether the string is of type int
</summary>
<param name= "Val" ></param>
<returns></returns>
public static bool Isvalidint (string val)
{
Return Regex.IsMatch (val, @ "^[1-9]d*.") [0]*$ ");
}

<summary>
Detects whether a string is all positive integers
</summary>
<param name= "str" ></param>
<returns></returns>
public static bool Isnum (String str)
{
BOOL B