Storing text of richtextbox in sqlite table in wpf

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WPF

SQLite

Here is my Query :
string Query = "Insert into Customer_New ( Opening_Date, Joining_Date, Clients_Title, Card_Number,Key_Person,Address_Current) Values('" + this.Date_Joining.Text + "','" + this.date_open.Text + "','" + this.txt_Title.Text + "','" + this.txt_cardnum.Text + "','" + this.txt_kperson.Text + "','" + this.rtf_caddress. _______+ "')";

Here "Address_Current" is rich text box .On property name i have placed dashed .Tell me how to store richtextbox text into data base table Customer_New ?