Ref or out how to set it as object

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I have a Method Thad Fill Data to Grid and return by ref data adapter object to able me to update data in grid after row update ...
and i Mad a Method to Pass OLEDB or SQLDB data adapter Variable
but when I use a ref or Out to Data Adapter error appear

What I have tried:

this a code from Method

enum ConnectionType
  {
      SQL,
      OLEDB
  }

public void Grid(ConnectionType ADOType, GridControl obj, object cn, DataSet DS, ref object DA, ref DataTable DT, String DataTableName, string sqlString, params object[] Parameter) 
        {

            if (ADOType == ConnectionType.OLEDB)
            {
                DataManagerOLEDB DM_ = new DataManagerOLEDB();
                OleDbDataAdapter da =  (OleDbDataAdapter)DA; 
                DM_.SelectFromTable((OleDbConnection)cn, sqlString, DS, out da, 
                DataTableName, Parameter);
            }
            else
            {
                DataManagerSQL DM_ = new DataManagerSQL();
                SqlDataAdapter da = (SqlDataAdapter)DA;

                DM_.SelectFromTable((SqlConnection)cn, sqlString, DS, out da, 
                DataTableName, Parameter);
            }
            
            DT = DS.Tables[DataTableName];
            obj.DataSource = DT;

when Pass Method like This

<pre>SurveyVar.fillDxControl.Grid(ConnectionType.OLEDB, grdSurvey, SurveyVar.cnSurvey, SurveyVar.DataSetSurvey, ref SurveyVar.DataAdapterSurvey,  ref datSurvey, "T002", sqlString, vParameters);

Error appear on data adapter variable as "

Severity	Code	Description	Project	File	Line	Suppression State
Error	CS1503	Argument 5: cannot convert from 'ref System.Data.OleDb.OleDbDataAdapter' to 'ref object'	Survey	F:\BannaSQLSource\_New Application\Source Code\SurveyApplication\Application Caption\forms\frmSurvey.cs	125	Active

Posted 21-Feb-18 0:41am

ibrahim maher

Updated 21-Feb-18 1:22am

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OriginalGriff · Accepted Answer · 2018-02-21T01:22:00

Let's simplify this a little:

C#

private void MyMethod(ref object o)
    {
    }
private void MyButton_Click(object sender, EventArgs ew)
    {
    OleDbDataAdapter da = new OleDbDataAdapter();
    MyMethod(ref da);
...

Why do you get an error saying:

cannot convert from 'ref System.Data.OleDb.OleDbDataAdapter' to 'ref object'

Think about it: o is a reference to an object, so you can very legitimately put any type of value into it inside the method:

C#

private void MyMethod(ref object o)
    {
    o = "hello";
    }

If the system allowed you to do that, what effect would it have?

Unpleasant, that's what. Because o is a ref, any changes to it are reflected in the calling method parameters variables -= in this case, da gets set to a string. So when control goes back to the button click event and the code tries to use the data in the DataAdapter, it finds a string and everything starts to fall over.

As a result, you can't cast a ref parameter - the type must match exactly.
If you need to pass different object types as ref parameters, then consider using generics instead.