Dynamics 365 Business Central: How to quickly get Longest Common Substring in AL

Hi, Readers.
Today I would like to share another mini tip about Business Central, how to quickly get Longest Common Substring in AL.
In computer science, a longest common substring of two or more strings is a longest string that is a substring of all of them. For example, the strings “ABABC”, “BABCA” and “ABCBA” have only one longest common substring, viz. “ABC” of length 3. Other common substrings are “A”, “AB”, “B”, “BA”, “BC” and “C”. More details in wiki: Longest common substring

This isn’t that simple if we write it from scratch in AL, so is there any easy way? Yes. There is a standard method.
codeunit 1251 “Record Match Mgt.” -> procedure GetLongestCommonSubstring

Let’s look at a simple example. I create a test page, enter two strings and get the longest common substring.

Test01:

Test02:

Source code: Github

page 50200 "Get Longest Common Substring"
{
    PageType = Card;
    ApplicationArea = All;
    UsageCategory = Administration;

    layout
    {
        area(Content)
        {
            group(Input)
            {
                field(FirstString; FirstString)
                {
                    Caption = 'First String';
                    ApplicationArea = All;
                    trigger OnValidate()
                    begin
                        if FirstString = '' then
                            LongestCommonSubstring := '';
                        GetLongestCommonSubstring();
                    end;
                }
                field(SecondString; SecondString)
                {
                    Caption = 'Second String';
                    ApplicationArea = All;

                    trigger OnValidate()
                    begin
                        if SecondString = '' then
                            LongestCommonSubstring := '';
                        GetLongestCommonSubstring();
                    end;
                }
            }
            group(Result)
            {
                field(LongestCommonSubstring; LongestCommonSubstring)
                {
                    Caption = 'Longest Common Substring';
                    ApplicationArea = All;
                    Editable = false;
                }
            }
        }
    }
    var
        FirstString: Text;
        SecondString: Text;
        LongestCommonSubstring: Text;

    local procedure GetLongestCommonSubstring()
    var
        RecordMatchMgt: Codeunit "Record Match Mgt.";
    begin
        if (FirstString <> '') and (SecondString <> '') then
            LongestCommonSubstring := RecordMatchMgt.GetLongestCommonSubstring(FirstString, SecondString);
    end;
}

It’s very simple, so what should you do if you want to input 3 strings? Because this is an intersection, we only need to execute procedure GetLongestCommonSubstring once more. For example,

Test:

Great, give it a try!!!😁

Source code: Github

page 50200 "Get Longest Common Substring"
{
    PageType = Card;
    ApplicationArea = All;
    UsageCategory = Administration;

    layout
    {
        area(Content)
        {
            group(Input)
            {
                field(FirstString; FirstString)
                {
                    Caption = 'First String';
                    ApplicationArea = All;
                    trigger OnValidate()
                    begin
                        if FirstString = '' then
                            LongestCommonSubstring := '';
                        GetLongestCommonSubstring();
                    end;
                }
                field(SecondString; SecondString)
                {
                    Caption = 'Second String';
                    ApplicationArea = All;

                    trigger OnValidate()
                    begin
                        if SecondString = '' then
                            LongestCommonSubstring := '';
                        GetLongestCommonSubstring();
                    end;
                }
                field(ThirdString; ThirdString)
                {
                    Caption = 'Third String';
                    ApplicationArea = All;

                    trigger OnValidate()
                    begin
                        if SecondString = '' then
                            LongestCommonSubstring := '';
                        GetLongestCommonSubstring();
                    end;
                }
            }
            group(Result)
            {
                field(LongestCommonSubstring; LongestCommonSubstring)
                {
                    Caption = 'Longest Common Substring';
                    ApplicationArea = All;
                    Editable = false;
                }
            }
        }
    }
    var
        FirstString: Text;
        SecondString: Text;
        ThirdString: Text;
        LongestCommonSubstring: Text;

    local procedure GetLongestCommonSubstring()
    var
        RecordMatchMgt: Codeunit "Record Match Mgt.";
    begin
        if (FirstString <> '') and (SecondString <> '') and (ThirdString <> '') then
            LongestCommonSubstring := RecordMatchMgt.GetLongestCommonSubstring(RecordMatchMgt.GetLongestCommonSubstring(FirstString, SecondString), ThirdString);
    end;
}

END

Hope this will help.

Thanks for reading.

ZHU