You don't have to "predeclare" methods like you do in C: so replace teh semicolon with curly brackets to create an empty constructor:
public class clsDSLApp : clsDSLBase
{
public clsDSLApp() {}
public bool FillComboBoxDataSet(ref ComboBox cboComboBox, DataSet dsRecords, int intDisplayMemberColumnIndex, int intValueMemberColumnIndex);
public bool FillComboBoxSQL(ref ComboBox cboComboBox, string strSQL, int intConnectionIndex, int intDisplayMemberColumnIndex, int intValueMemberColumnIndex);
public bool FillComboBoxSQL(ref ComboBox cboComboBox, string strSQL, string strConnectionString, int intDisplayMemberColumnIndex, int intValueMemberColumnIndex);
public bool FillComboBoxXML(ref ComboBox cboComboBox, string strXMLFileName, string strSQL, int intConnectionIndex, bool blnRecreateXML, int intDisplayMemberColumnIndex, int intValueMemberColumnIndex);
}
Or, to have exactly the same effect, just delete the line!
public class clsDSLApp : clsDSLBase
{
public bool FillComboBoxDataSet(ref ComboBox cboComboBox, DataSet dsRecords, int intDisplayMemberColumnIndex, int intValueMemberColumnIndex);
public bool FillComboBoxSQL(ref ComboBox cboComboBox, string strSQL, int intConnectionIndex, int intDisplayMemberColumnIndex, int intValueMemberColumnIndex);
public bool FillComboBoxSQL(ref ComboBox cboComboBox, string strSQL, string strConnectionString, int intDisplayMemberColumnIndex, int intValueMemberColumnIndex);
public bool FillComboBoxXML(ref ComboBox cboComboBox, string strXMLFileName, string strSQL, int intConnectionIndex, bool blnRecreateXML, int intDisplayMemberColumnIndex, int intValueMemberColumnIndex);
}
An empty constructor will be created for you behind the scenes.