Substring problem

Keve G??borKeve G??bor hungary
edited 1:24AM in FastReport .NET
Hello!

In the attached example, you can see 2 textobject. The green one working fine, but the red one not.
If i change the Parameter1 Expression property to nothing from "", the red one working fine. But if the property value "", the report engine say:
Inner exception:
startIndex cannot be larger than lenght of the string
Parameter name startIndex

red Text object value:

[IIf(Length([Parameter1])>0,Substring([Parameter1],1,1),[Parameter2])]

Can you explain me, what the problem of this expression?

Thanks!

Comments

  • StarkStark Syria
    edited August 2010
    Hi , have a good day

    The Error is very clear , I will try to Explain it in details :

    1) This One "Substring([Parameter1],1,1)" is try to select a string from paramter1
    Which start with character of index 1 and end at character of index 1

    For Example :
    if paramter1 = "Stark" then SubString([paramter1], 1,1) will give the result "t"
    BUT
    if paramter1 = "" then SubString([paramter1], 1,1) will throw an error because there is no character at Index 1 , paramter1 has Zero Characters

    And in your Attachment report Parameter1 = "" , and that is why you get an error !


    Solution :

    you have two ways :
    *) Give Paramter1 some value ,
    OR
    *) replace the SubString([paramter1], 1,1) With SubString([paramter1], 0,0)



    Hope this help




    P.S :
    I didn't know what are you trying to achieve , or why paramter1 has the value "" ?
  • Keve G??borKeve G??bor hungary
    edited August 2010
    Hello Stark!

    Thanks the answer!

    You right! But...

    I think that due the IIf condition, the Substring procedure should not be evaluate, because the Parameter1 length = 0.

    The right evaluation order is:

    <!--fonto:Courier New--><span style="font-family:Courier New"><!--/fonto-->IIf -> Length(Parameter1)>0 -> false -> Parameter2
    -> true -> Substring(Parameter1,1,1)<!--fontc--></span><!--/fontc-->

    If Parameter1 value is "" then Lenght(Parameter1) = 0.

    But i think the real evaluation start within.

    So, clarifying my question:
    Why evaluate the Substring function the engine, if Parameter1.Lengt()==0?

    [img]style_emoticons/<#EMO_DIR#>/unsure.gif" style="vertical-align:middle" emoid=":unsure:" border="0" alt="unsure.gif" /> regards, Gabor Keve[/img]
    Stark wrote: »
    Hi , have a good day

    The Error is very clear , I will try to Explain it in details :

    1) This One "Substring([Parameter1],1,1)" is try to select a string from paramter1
    Which start with character of index 1 and end at character of index 1

    For Example :
    if paramter1 = "Stark" then SubString([paramter1], 1,1) will give the result "t"
    BUT
    if paramter1 = "" then SubString([paramter1], 1,1) will throw an error because there is no character at Index 1 , paramter1 has Zero Characters

    And in your Attachment report Parameter1 = "" , and that is why you get an error !


    Solution :

    you have two ways :
    *) Give Paramter1 some value ,
    OR
    *) replace the SubString([paramter1], 1,1) With SubString([paramter1], 0,0)



    Hope this help




    P.S :
    I didn't know what are you trying to achieve , or why paramter1 has the value "" ?
  • StarkStark Syria
    edited August 2010
    You are welcome !
    I think that due the IIf condition, the Substring procedure should not be evaluate, because the Parameter1 length = 0.
    I was think the same , Until I saw your Question , because C# didn't do that
    string res = string.Empty;
    string paramter1 = "";
    string paramter2 = "text";
           
    res = paramter1.Length > 0 ? paramter1.Substring(1, 1) : paramter2;
    Console.WriteLine(res);
    

    So, clarifying my question:
    Why evaluate the Substring function the engine, if Parameter1.Lengt()==0?

    I think this is how fast report works , I really don't know much about it's engine , ( I am just a user for fast-report [img]style_emoticons/<#EMO_DIR#>/rolleyes.gif" style="vertical-align:middle" emoid=":rolleyes:" border="0" alt="rolleyes.gif" /> ) May be one of the makers can answer you ,[/img]

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