memory management and variables

Note that theLizard is someone that enjoys doing it himself, and that is good. Some people prefer to get help from others and for them, it is best to use the tools provided by Microsoft. I hope you read my article Database Table Update in a DataGridView without Writing Code.

Hi John,

I actually wrote that piece about 4 years ago, it is part of much larger collection of functions, methods and custom controls, Sam is right about MS doing similar program but it is your choice weather to use the MS x-spurts code or write your own to learn how it is done by those x-spurts, I prefer to write my own code that way I can deal with the side effects of the code whereas using some one else's code that you can't get to, you can't and will forever be writing work around code to solve problems you should not have to.

To be a good programmer you need to open your mind and to work outside the box if you only work within the box you only ever see what is in the box, not outside it.

If someone says you can't do that in programming, turn around and do it, if you have to use a third party control to make your job easier, think to yourself, can I make that control myself and learn some more by doing so.

When I wrote my controls using C#2005 it was my second major C# project, the first I learn't the  basics c# in web design.

You learn much more by doing things yourself than by using someone else's code, you get to learn the fundamentals by using sql to open tables and get the data from those tables without using a table adapter and filling grids dynamically without using data source  objects.

Here is another piece of code for you..

 //------------------------------------------------------------------------
  internal string createInsertWithValues(string groupName)
    {
    int gIndex = GetControlGroupIndexByName(groupName);
    string valuePart = "";
    string ctrlName = "";
    string value = "";
    string sTmp="(";
    if(gn[gIndex].GroupSqlInsert == null){
      MessageBox.Show("Could not create Insert Statement ..., Aborting", "Stop", MessageBoxButtons.OK, MessageBoxIcon.Stop);
      return("Aborted");
      }
    if(gn[gIndex].GroupSqlInsert != ""){
      //dose this record depend on a parent id?
      bool isGroupDependant = gn[gIndex].GroupDependant;
      int parentId = -1;
      if(isGroupDependant){
        parentId = getGroupRecordId(gn[gIndex].DependantGroupName);
        }
      else{
        if(gn[gIndex].ParentRecordId !=-1)
          parentId = gn[gIndex].ParentRecordId; 
        }
   
      //get value part of statement
      valuePart = gn[gIndex].GroupSqlInsert.Substring(gn[gIndex].GroupSqlInsert.IndexOf("VALUES(")+7);
      if(valuePart.Substring(valuePart.Length-1,1)== ")")  
        valuePart = valuePart.Substring(0, valuePart.Length-1);  //get rid of the ) at end of string       
      if(valuePart.Contains("#")){
        string a = valuePart.Substring(0, valuePart.IndexOf(","));
        valuePart = valuePart.Replace(a, "");
        valuePart = valuePart.Trim();
        if(valuePart.Substring(0, 1) == ","){ valuePart = valuePart.Substring(1); }
       
        a = a.Replace("#", "");
        sTmp += a + ", ";
        }
        valuePart = valuePart.Trim();
      while(valuePart.IndexOf("@") >= 0){  // as long as there is an @ in the string
        //get the control name from the string and strip the @ indicator
        //and the last ' if it exists
        int start, end;
        start = valuePart.IndexOf("@")+1;  //get ctrl name start
        end = valuePart.IndexOf(",")-1;    //get ctrl name end
        if(end <= 0)
          end = valuePart.Length-1;        //get ctrl name if no , found
       
        ctrlName = valuePart.Substring(start, end);  //get value from ctrl

        if(valuePart.IndexOf(",") > 0)
          valuePart = valuePart.Remove(start-1, valuePart.IndexOf(",")+1);
        else
          valuePart = valuePart.Remove(start-1, valuePart.Length);

        value =  getControlData(gIndex, ctrlName);
        value = common.checkSingleQuote(value);
        sTmp +=  value + ",";
        }
      }
    if(sTmp.Substring(sTmp.Length-1, 1) == ","){
      sTmp = sTmp.Remove(sTmp.Length-1);
      sTmp += ")";
      }
    else{
      sTmp += sTmp.Substring(1, sTmp.Length-1) + ")";
      }
    valuePart = sTmp;
    //re-construct insert statement
    sTmp = gn[gIndex].GroupSqlInsert.Substring(0, gn[gIndex].GroupSqlInsert.IndexOf("VALUES"));
    sTmp += "VALUES" + valuePart;
    gn[gIndex].GroupSqlInsert = sTmp;
    return(sTmp);
 }
 //------------------------------------------------------------------------

Microsoft has already done programming similar to what theLizard has done; you should use the programming that the Microsoft experts have done for you.

hey guys,

thanks for the replies and thanks for taking the time to type all that out theLizard.

most of that still is unjnown to me, however; i have copied all of it and when i get more skilled im going to look back at it again  and it will be put to good use.

the main thing for now is that i can directly assign the value and all those other things that have been mentioned i have saved and will revise and look at once im upto speed on that sort of level :)

Hi John,

My first question is how are you getting the data from the db?

My second question is do you want to know the lazy way or the slightly longer programming way where you control all aspects of your program.

The longer way allows you to create a class which can be instantiated a number of times within a single form

Assigning db values to variables is what I do in almost all situations but then I do not declare individual variables to accommodate every text box, combo box etc..

What I do is something like

(a)  create a class say recordValues

(b) in this class you create a struct of say, fieldProperties which would contain something like

  int      datatype;
  string fieldName;
  string fieldValue;

(c) in the same class declare an array of fieldProperties with 0 elements  ie fieldProperties[] fieldProps = new fieldProperties[0];

in your form you can then instantiate your class any number of times to represented any number of tables you want to assign field values.but this requires you to make your own db connections and loop through the result set and assign each value to a new element of fieldProps.

I am putting this code in for example only do not even try to compile it, it will not work no matter what you do to it, this is one function of many others that is needed to do what it does

In simple terms, this is one of many functions of a control that when placed on a form will load records (show in text boxes etc.), edit or delete without writing any code on the form to do so, it does need custom controls derived from the standard controls with additional properties though.  I put this here simply to show how complex things can be when you do things the long way, the upside is that you only do these things once and can then use in any other project you want simply by dropping the controls on your forms.

try to read it and work out what it is doing, if you want answers to parts you don't understand let me know.

  internal static bool getRecord(lizardControlAgent fg, int gIndex)
    {
    int i=0;
    int ctrlCount = fg.gn[gIndex].GroupCount;
    string TableName = fg.gn[gIndex].TableName;
    string sql = "SELECT ";
    string field = "";
    bool allowNull = true;
    object value = null;
    lizardSQLSource sqlSource = new lizardSQLSource();
    if(fg.gn[gIndex].WantGroupRecordId){
       sql += fg.gn[gIndex].RecordIdFieldName + ", ";}
      
    for(i = 0; i       object c = fg.gn[gIndex].Ctrl[i];
      //get control column Name and build sql statement
      sql += fg.getColumnName(c);
      if(i < ctrlCount-1){
        sql += ",";
        }
      }
    //add FROM part
    sql += " FROM " + TableName;
   
    //do we want a where part
    if(fg.gn[gIndex]._sqlWhereForGet != ""){
      sql += " " + fg.gn[gIndex]._sqlWhereForGet;
      }
   
    fg.SqlDataSource.SqlStatement = sql;
    fg.SqlDataSource.Command =  fg.SqlDataSource.newCommand(fg.SqlDataSource.ServerSource, sql);
    
    if (fg.SqlDataSource.Command == null || !fg.SqlDataSource.ExecuteReader(fg.SqlDataSource.Command))
      return(false);
   
    if(fg.SqlDataSource.read())
      {
      if(fg.gn[gIndex].WantGroupRecordId){
        if(fg.gn[gIndex].RecordIdFieldName != ""){
          fg.gn[gIndex].GroupRecordId = int.Parse(fg.SqlDataSource.get(fg.gn[gIndex].RecordIdFieldName));
          }
        }
      for(i = 0; i         object c = fg.gn[gIndex].Ctrl[i];
        field = fg.getColumnName(c).ToString();
        //set allow null here
        sqlSource.ServerSource = fg.SqlDataSource.ServerSource;
        sqlSource.sqlConnect = true;
        allowNull = fg.SqlDataSource.AllowNull(fg.gn[gIndex].TableName, field, sqlSource);
        fg.setNullable(c, allowNull);     
        value = (object)fg.SqlDataSource.get(field);
        value = setValueByDataType(value, getDataType(sqlSource, field, TableName));
        fg.ctrlSetValue(c, value);
        }
      }
    fg.SqlDataSource.terminate();
 
  return(true);
  }

It is good design to do what you are suggesting; to put the data into and get it from a separate variable but to do it using the best design is a bit complicated for a beginner. There is so much to learn that you can just go ahead and do it the easier way for now. In other words, go ahead and use just the Text property of the Textbox control. Use of a separate variable would be best depending on how you got the data; whetehr the data is being read from a database of someplace else. You could use a TableAdapter to read the data from the database and write to the database and then you can bind the form to the TableAdapter and then .Net will take care of putting the data on the form and getting it from the form.
 
Some people will say you should use a local variable instead of a property of the control, but I do not think that makes a difference.

hey Santosh, thanks for the reply.

i have now publish my app but now discovered a problem.

EDIT** when i delete one of the records by clicking on the red X i get an error message saying Concurrency Violation: the DeleteCommand affected 0 of the expected 1 records.


why might this apear? i cant seem to get it to go away, i even built my program from scratch again but same thing. i dont know if it has anything to do with the button i added that simply populates the textboxes for me?