Perform some check routines before enabling the "Import"-button.

source/loaddata.dfm

@@ -28,6 +28,7 @@ object loaddataform: Tloaddataform
     Anchors = [akRight, akBottom]
     Caption = 'Import!'
     Default = True
+    Enabled = False
     ModalResult = 1
     TabOrder = 0
     OnClick = btnImportClick
@@ -77,6 +78,7 @@ object loaddataform: Tloaddataform
           Anchors = [akLeft, akTop, akRight]
           TabOrder = 0
           Text = 'editFilename'
+          OnChange = editFilenameChange
           OnDblClick = btnOpenFileClick
         end
         object btnOpenFile: TBitBtn

source/loaddata.pas

@@ -52,6 +52,7 @@ type
     editLineTerminator: TEdit;
     lblLineTerminator: TLabel;
     lblIgnoreLines: TLabel;
+    procedure editFilenameChange(Sender: TObject);
     procedure btnCancelClick(Sender: TObject);
     procedure FormShow(Sender: TObject);
     procedure comboDatabaseChange(Sender: TObject);
@@ -187,6 +188,9 @@ begin
   // select all:
   for i:=0 to chklistColumns.Items.Count-1 do
     chklistColumns.checked[i] := true;
+
+  // Ensure valid state of Import-Button
+  editFilenameChange(sender);  
 end;
 
 
@@ -327,4 +331,20 @@ begin
     end;
 end;
 
+
+
+{** Make "OK"-button only clickable if
+ - filename is not empty
+ - table is selected
+ - columnnames could be fetched normally
+ - filename exists
+}
+procedure Tloaddataform.editFilenameChange(Sender: TObject);
+begin
+  btnImport.Enabled := (editFilename.Text <> '')
+    and (chklistColumns.Items.Count > 0)
+    and (FileExists(editFilename.Text));
+end;
+
+
 end.