WinForm Small program------Keep n-bit rounding decimals

One: You can choose to retain the number of digits, the comments are explained very detailed,

Two: All code

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel;usingSystem.Data;usingSystem.Drawing;usingSystem.Linq;usingSystem.Text;usingSystem.Windows.Forms;namespaceround{ Public Partial classFrm_main:form { PublicFrm_main () {InitializeComponent (); }        Private voidBtn_get_click (Objectsender, EventArgs e) {            DoubleP_dbl_d1, P_DBL_D2;//define two variables of type double            if(Double. TryParse (TXT_ADD1. Text, outP_DBL_D1) &&//determine if the input information is correct                Double. TryParse (TXT_ADD2. Text, outp_dbl_d2)) {txt_add3. Text=//The value after rounding is obtainedRound (p_dbl_d1 + p_dbl_d2, Cbox_select. SelectedIndex +1).            ToString (); }            Else{MessageBox.Show (//Prompt for error messages                    "The input value is not correct! ","Tips! "); }        }        /// <summary>        ///method for calculating the rounding of double values/// </summary>        /// <param name= "dbl" >numeric value for rounding of calculated results</param>        /// <param name= "I" >Reserved decimal digits</param>        /// <returns>returns the double value after rounding</returns>        Internal DoubleRound (DoubleDblinti) {stringP_str_dbl = Dbl. ToString ();//converts a double value to a string            stringP_str_lower =//converts a double numeric decimal bit to a stringP_str_dbl. Split ('.')[1];//----------get '. ' After the character, (this usage on the net has little relevant material)            intP_str_length = P_str_lower. Length;//To calculate a double numeric decimal digit lengthDbl+ = GetValue (i, p_str_length);//to start rounding operationsP_str_dbl = Dbl. ToString ();//converts the value after an operation to a string            if(P_str_dbl. Contains ("."))//determine if there are decimal digits            {                stringP_str_upper =//To get an integer digit stringP_str_dbl. Split ('.')[0];//----------get '. ' The previous characterP_str_lower = P_str_dbl. Split ('.')[1];//get the decimal digit string                if(P_str_lower. Length > I)//determine if the number of digits is greater than the number of reserved decimal digits{p_str_lower= P_str_lower. Substring (//intercept reserved decimal digits                        0, i); return Double. Parse (//returns a Double valueP_str_upper +"."+p_str_lower); }                Else                {                    return Double. Parse (P_STR_DBL);//returns directly if the number of digits is less than the number of reserved decimal digits                }            }            Else            {                return Double. Parse (P_STR_DBL);//return the value directly if there are no decimal digits            }        }        /// <summary>        ///returns a decimal number for the next digit of 5, such as 4 decimal places, that is required to be retained, i.e. 0.0005/// </summary>        /// <param name= "Int_null" >rounding a reserved number of digits</param>        /// <param name= "Length" >Number of decimal digits of the original data</param>        /// <returns>returns a decimal value for rounding calculations</returns>        Internal DoubleGetValue (intInt_null,intlength) {            stringP_str_dbl ="0.";//define a string variable and assign a value             for(inti =0; i < length; i++)//adding decimal digits with A for loop            {                if(I > Int_null-1) {P_str_dbl+="5";//Add 5 to the rounding portion of the decimal                }                Else{P_str_dbl+="0";//add 0 to the reserved portion of the decimal                }            }            return Double. Parse (P_STR_DBL);//returns the decimal value        }        Private voidFrm_main_load (Objectsender, EventArgs e) {Cbox_select. SelectedIndex=0;//Cbox_select Control selects the first item by default        }    }}