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How to change text dynamic in unity

at line 161,I want to insert my text in parameter t,but it won't change when i debug it.although the parameter tmp had alredy changed.
I want to change this Text in UI,when my parameter t changes.

With respect to your specific issue, Insert is defined as:
public string Insert (int startIndex, string value);
and returns a new string. In C#, strings aren't modified, new strings are created. In this way, they act like a value type, even though they're a reference type. In other words, once a string is created, it is never modified - it's 'immutable'. So, you need to store your newly created string.
In cases like this, I like to use the string interpolation, as it allows me to get a slightly clearer representation of what the final string will look like.
var tmp = System.Text.Encoding.UTF8.GetString ( e.Message );
t.text = $"{tmp}\n{t.text}"; // Note that a newline is represented as \n
Or, if you add the System.Text namespace; you could reduce it down to:
using System.Text;
...
t.text = $"{Encoding.UTF8.GetString ( e.Message )}\n{t.text}";

The string type in c# is immutable, therefore Insert returns a new string instead of modifying the current one.
Do:
t = t.text.Insert(0, tmp + "//n");
See also
How to modify string contents in C#

Format String to Match Specific Pattern

I am trying to figure out how to format a string to a specific pattern.
When a user is entering their employee id number, they often get confused on what is expected from them. Because they are often told that their employee id is either a 5 digit or 4 digit number depending on when they were hired.
For example, my employee id number is E004033 but for most of our systems, I just have to enter 4033 and the system will find me.
We are trying to add this to one of our custom pages. Basically what I want to do is format a string to always look like E0XXXXX
So if they enter 4033 the script will convert it to E004033, if they enter something like 0851 it will convert it to E000851 or if they enter 11027 it will convert it to E011027
Is there a way basically add padding zeros and a leading E if they are missing from the users input?

You can simply:
var formattedId = "E" + id.PadLeft(6, '0');
To remove an existing leading E(s)
var text = "E" + val.TrimStart(new[] {'E'}).PadLeft(6, '0');

Make sure the user's input is an integer, then format to 6 spaces using String.Format.
int parsedId;
bool ok = int.TryParse(id, out parsedId);
if (ok)
{
return String.Format("E{0:000000}", parsedId);
}

C# Regex.Match to decimal

I have a string "-4.00 %" which I need to convert to a decimal so that I can declare it as a variable and use it later. The string itself is found in string[] rows. My code is as follows:
foreach (string[] row in rows)
{
string row1 = row[0].ToString();
Match rownum = Regex.Match(row1.ToString(), #"\-?\d+\.+?\d+[^%]");
string act = Convert.ToString(rownum); //wouldn't convert match to decimal
decimal actual = Convert.ToDecimal(act);
textBox1.Text = (actual.ToString());
}
This results in "Input string was not in a correct format." Any ideas?
Thanks.

I see two things happening here that could contribute.
You are treating the Regex Match as though you expect it to be a string, but what a Match retrieves is a MatchGroup.
Rather than converting rownum to a string, you need to lookat rownum.Groups[0].
Secondly, you have no parenthesised match to capture. #"(\-?\d+\.+?\d+)%" will create a capture group from the whole lot. This may not matter, I don't know how C# behaves in this circumstance exactly, but if you start stretching your regexes you will want to use bracketed capture groups so you might as well start as you want to go on.

Here's a modified version of your code that changes the regex to use a capturing group and explicitly look for a %. As a consequence, this also simplifies the parsing to decimal (no longer need an intermediary string):
EDIT : check rownum.Success as per executor's suggestion in comments
string[] rows = new [] {"abc -4.01%", "def 6.45%", "monkey" };
foreach (string row in rows)
{
//regex captures number but not %
Match rownum = Regex.Match(row.ToString(), #"(\-?\d+\.+?\d+)%");
//check for match
if(!rownum.Success) continue;
//get value of first (and only) capture
string capture = rownum.Groups[1].Value;
//convert to decimal
decimal actual = decimal.Parse(capture);
//TODO: do something with actual
}

If you're going to use the Match class to handle this, then you have to access the Match.Groups property to get the collection of matches. This class assumes that more than one occurrence appears. If you can guarantee that you'll always get 1 and only 1 you could get it with:
string act = rownum.Groups[0];
Otherwise you'll need to parse through it as in the MSDN documentation.

How to retrieve 0 as the first number in C#

scenario:
I have a database having a record 001234 and I am calling it with cmd.executescaler(); into a int variable. The problem is when I retrieve the saved data (001234) data from that variable it gives only 1234. 00 in 001234 are important, this was the problem first coming in db where sql omits the first zero's then I changed the datatype to nvarchar which works, how I can retrieve the data on the form exactly 001234.
Note: I cannot take the data into string as I have to also apply some calculations on them.
using Sql Server visual studio 2010 c#
Hope it is clear not vague. If you need more information tell me.
Thanks in advance.

Numeric datatype don't have and can't have leading zeros. So the only way to have leading zeros is to store the value as a string.
However, this is just a matter of formatting the output that is shown to the user. You can read the database value into an int variable, do your calculations and when showing the value, you can do:
string displayValue = String.Format("{0:D6}", intValue);
and show the value of displayValue.

If you want to work on the Code side:
string displayValue = String.Format("{0:D6}", intValue);
If you want to work on the DB side you need a Pad function that allows to write this kind of query:
SELECT dbo.PadString ('8', '0', 5)
->Result: 00008
SELECT dbo.PadString ('abc', '*', 12)
->Result: *********abc
SELECT dbo.PadString ('abc', '0', 7)
->Result: 0000abc
Create a function in T-SQL
CREATE FUNCTION [dbo].[PadString]
(#Seq varchar(16),
#PadWith char(1),
#PadLength int
)
RETURNS varchar(16) AS
BEGIN
declare #curSeq varchar(16)
SELECT #curSeq = ISNULL(REPLICATE(#PadWith, #PadLength - len(ISNULL(#Seq ,0))), '') + #Seq
RETURN #curSeq
END

If those leading zeros have some meaning and can't be left out, conversion can be done:
int number = 0;
string strNumber = (string)cmd.ExecuteScalar();
if(int.TryParse(strNumber, out number))
{
// process number
// if you want some output to be formatted with leading
// zeros you can use PadLeft method
int totalNumberOfDigits = 6;
string strResult = number.ToString().PadLeft(totalNumberOfDigits, '0');
}

you can use string.PadLeft() in c# after retrieving your number, as you have fixed length numbers
example from msdn,
string str = "forty-two";
char pad = '.';
Console.WriteLine(str.PadLeft(15, pad)); // Displays "......forty-two".
Console.WriteLine(str.PadLeft(2, pad)); // Displays "forty-two".

The reason SQL does this is because 001234 = 1234 in any number format no matter what type it is. As a "Dirty" solution you could cast it as an int which will give you 1234, perform your calculations and then cast your answer back to string adding the leading zeros.
int myValue = Int32.Parse("001234");
int myAnswer = myValue * 2;
string myAnswerString = "00" + myAnswer.ToString();
The best way to go though would be to format your string as suggested by #Thorsten Dittmar. If possible, do not store numeric values in the database as varchar to begin with, however I know that this is sometimes a requirement, but the I cannot see the point on doing calculations on those values.

Pick a value using a regular expression

I have a string in the format:
PROVIDER=Sybase.ASEOLEDBProvider.2;User ID=sa;Server Name=UKServer;Server Port Address=5001;Initial Catalog=master
Using a regular expression in C# now can I get the value of Server Name?
Please note that Server Name could be in any location in the string and there may or may not be a space either side of the "=" i.e. the fomate could be
... Server Name=UKServer;....
... Server Name = UKServer;....
... Server Name =UKServer;....
... Server Name= UKServer;....

You don't really have to the parse the connection-string yourself; the handy OdbcConnectionStringBuilderclass can do it for you. It implementsIDictionary, allowing you retrieve all of the attributes of the connection-string by key. I'm sure it is reasonably resistant to the different kinds of input that you mention, e.g. additional white-space, different ordering of key-vale pairs, etc.
Here's an example, tested for your sample:
var connString = #"PROVIDER=Sybase.ASEOLEDBProvider.2;User ID=sa;Server Name=UKServer;Server Port Address=5001;Initial Catalog=master";
var connStringBuilder = new OdbcConnectionStringBuilder(connString);
var serverName = connStringBuilder["Server Name"].ToString();

_serverName = RegEx.Match(inputString, "Server Name ?= ?([\\w]+);").Groups(1).Value;
Breakdown:
Server Name ?= ? // Normal string, the ? means that the preceding character
// or group is optional (0 or 1)
([\w]+); // The parentheses define a group (the Group(0) is the
// always the whole match), so that you can easily get a
// substring of the match.
[\w]+ // Matches any alphabetical character, number or underscore

Something like this should work:
"Server Name\s*=\s*(\w+)\s*;"

How about something like this :
[^&]*(i?)(Server Name\s|)((i?)[a-z]);
_serverName = RegEx.Match(inputString, "[^&]*(i?)(Server Name\s|)((i?)[a-z]);").Groups(2).Value;