C# - Replacing characters in a string

Question

I have a string that contains a login, database, and a password.

string str = "user Id=abc, database=DDD, Password=mypasswd"  

I want to be able to replace the database value "DDD" with a different value.

I tried using the string.Replace, but I won't know what the existing database will be.

Does anyone know of a simple solution?

Answer 1

Following is the only recommended way by MSDN to prevent Connection String Injection Attacks

http://msdn.microsoft.com/en-us/library/ms254947.aspx

// cs stores previous connection string which came from config

System.Data.SqlClient.SqlConnectionStringBuilder builder = 
    new System.Data.SqlClient.SqlConnectionStringBuilder(cs);
builder.InitialCatalog = "NEWDB";

// you get your database name replaced properly...
cs = builder.ToString();

Based on the type of database or database driver, you have to use different class, for MySql it should be MySqlConnectionStringBuilder and name of property might be Database.

Answer 2

One alternative is to use a Regex, this would do the replace for you:

using System.Text.RegularExpressions;

string cStr = "user Id=abc, database=DDD, Password=mypasswd";
Console.WriteLine(cStr);

Regex r = new Regex("(?<=database=)(.+?)(?=,)");
cStr = r.Replace(cStr, "NewDatabaseName");

Console.WriteLine(cStr);

NOTE: this was compiled, run, and proven with scriptcs so it's fairly droppable into your solution.

Answer 3

How about using String.Format ?

string username = "abc";
string database = "myDB";
string password = "my_pw";

string str = String.Format("user Id={0}, database={1}, Password={2}",
                           username, database, password);

You could then load these values (or even the whole connection string) from a configuration file.

Answer 4

Regexes are also an option:

string str = "user Id=abc, database=DDD, Password=mypasswd",
    newDatabase = "newDb";

Console.WriteLine( Regex.Replace( str, @"(?<=database=)(.*?)(?=,)", m => newDatabase ) );

Answer 5

Split the string at the comma separator, then take the second index of the resulting array, split at the equal separator, substitute the second element, then recombine all

string str = "user Id=abc, database=DDD, Password=mypasswd";
string[] parts = str.Split(',');
string[] dbparts = parts[1].Split('=');
dbparts[1] = "new_database_name";

parts[1] = string.Join("=", dbparts);
string final = string.Join(", ", parts);

and, well, with a bit of error checking would be safer.

Answer 6

Same as above but if you are fun of LINQ

string str = "user Id=abc, database=DDD, Password=mypasswd";

var q = from part in str.Split(new[] {','})
                let trimedPart= part.Trim()
                let replacedPart  =trimedPart.StartsWith("database=")?trimedPart.Replace("DDD","newValue"):trimedPart
                select replacedPart;

        var newConStr = q.Aggregate((current, next) => current + "," + next);

Answer 7

These solutions are all great, but doesn't one long and confusing line have a certain elegance?

"user Id=abc, database=DDD, Password=mypasswd".Substring(0, "user Id=abc, database=DDD, Password=mypasswd".IndexOf("database=")) + "database=" + "[YOUR VALUE HERE]" + ", " + "user Id=abc, database=DDD, Password=mypasswd".Substring("user Id=abc, database=DDD, Password=mypasswd".IndexOf("Password="))

Output: user Id=abc, database=[YOUR VALUE HERE], Password=mypasswd