How to get string name from other string in C#

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C#3.5

I am developing a SMS Software, i want to give Option to Customer to define their own SMS. I give them a text box to write their own SMS which can include database field names Like Dear Customer +CustName+ Thank you for visiting Here, Your Bill Amount is : +BillTotal+ CustNmae And BillTotal is Database Field name and Customer add All Other Field Name which i Show Him to Include. I want to get Field name from String and fill its value and send SMS to Customer. My English is not very well i Hope you understand what i want to say..

What I have tried:

queryacc = "SELECT Id, MessageType, Message, ModifyDate FROM PreDefineMessage where MessageType ='Sale'";
		query = "select * from customer where CustomerCode ='0001'";
		DataTable dtCust = Queries.runSQLCommandDataTable(query);
		DataTable test = runAccessQuerydt(queryacc);
		string messagepreDefine = string.Empty;
		foreach (DataRow  dr in test.Rows )
		{
			messagepreDefine = dr["Message"].ToString ();
			string ff = "Id";
			string f =  "+dr["+ff+"].ToString ()+" ;
			string oldmes = "Dear Customer Your id is : "+dr["Id"].ToString ()+"";
			oldmes = f;
			oldmes =oldmes .Insert (5,f);
			
			oldmes ="Dear customer your id is "	;
		}
		int indexp1 =messagepreDefine .IndexOf ('+');

		 messagepreDefine =messagepreDefine .Insert(indexp1+1, "dr[\"");
		 int indexp2 = messagepreDefine.IndexOf('+',indexp1+1 );
		 messagepreDefine = messagepreDefine.Insert(indexp2 + 1, "");
		foreach (DataRow dr in dtCust.Rows )
		{
			string newmessage = messagepreDefine;
		}