StringBuilder Object where you can point specific character but not in System.String

From sample code, you will see nice thing that can be useful in programming
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System.Text.StringBuilder sb = new System.Text.StringBuilder("Rat: the ideal pet");
sb.Append(" is caught");
sb[0] = 'C';
System.Console.WriteLine(sb.ToString());
System.Console.ReadLine();
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Output : Cat: the ideal pet is caught

Padding character before a string in sql query

select right(replicate(@padchar, @len) + @str, @len)
e.g. select right(replicate('0', 10) + 'hell boy', 10)

Expression evaluation in C#

Try with this code block which is faster than using codeDom
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static double Evaluate(string expression)
{
var loDataTable = new DataTable();
var loDataColumn = new DataColumn("Eval", typeof(double), expression);
loDataTable.Columns.Add(loDataColumn);
loDataTable.Rows.Add(0);
return (double)(loDataTable.Rows[0]["Eval"]);
}