VB..net code error free but same C# code gives error?

Question

I have converted my project from VB.net to C# using converter sw
Now i m facing some errors , which i try to remove
Here is the code in c# and vb.net also
But main thing is that it does not give error in vb.net
error is ,Error:- Use of unassingned local varialble "tmpYear"


        public void cmdSearch_Click(System.Object sender, System.EventArgs e)
        {
            try
            {
                frmStudentSearch dlgStudentSearch = new frmStudentSearch();
                int iStudentID;
                string strCboSelection;
                DataTable tmpDataTable;
                string strSQL;
                DataTable tmpYear;
                DataTable tmpData;
                DataTable tmpCboDataTable;
               
                dlgStudentSearch.ShowForm();
                //MsgBox("Student Fees" + vbCrLf + "iStudentID :: " + _CConstant._iStudentID.ToString)
                iStudentID = modMain._CConstant._iStudentID;
                if (iStudentID > 0)
                {
                    strCboSelection = "SELECT ID, Name FROM tblStudent";
                    tmpCboDataTable = modMain._CDatabase.GetDataTable(strCboSelection);
                    CboStudentName.SelectedValue = iStudentID.ToString();
                   
                    if (CboStudentName.Text.Trim().Length != 0)
                    {
                        strSQL = "SELECT BatchID FROM tblStudent ";
                        strSQL += "WHERE ID = " + CboStudentName.SelectedValue.ToString() + " ";
                        tmpYear = modMain._CDatabase.GetDataTable(strSQL);
                        if (tmpYear.Rows.Count > 0)
                        {
                            if (Information.IsDBNull(tmpYear.Rows[0]["BatchID"]) == true)
                            {
                                Interaction.MsgBox("Batch Not Present For This Student", MsgBoxStyle.Information, null);
                                cmdSave.Enabled = false;
                                return;
                            }
                            else
                            {
                                cmdSave.Enabled = true;
                            }
                        }
                    }
                   
                    strSQL = "SELECT ClassID,SectionID FROM tblStudentDetail ";
                    strSQL += "WHERE StudentID = " + CboStudentName.SelectedValue.ToString() + " ";
                    strSQL += "AND OrganizationID = " + modMain._CVariable._ORGANIZATIONID.ToString() + " ";
                    tmpDataTable = modMain._CDatabase.GetDataTable(strSQL);
                    if (tmpDataTable.Rows.Count == 0)
                    {
                        Interaction.MsgBox("No Student Details Present For This Student", MsgBoxStyle.Information, null);
                        cmdSave.Enabled = false;
                        return;
                    }
                    else
                    {
                        cmdSave.Enabled = true;
                    }
                   
                    if (cmdSave.Enabled == true)
                    {
                        strSQL = "SELECT Amount FROM tblLibraryStaticFees ";
                        strSQL += "WHERE BatchID = " + tmpYear.Rows[0]["BatchID"].ToString() + " ";
//In the above line of code it says that ,Error:- Use of unassingned local varialble "tmpYear"
                        strSQL += "AND ClassID = " + tmpDataTable.Rows[0]["ClassID"].ToString() + " ";
                        strSQL += "AND SectionID = " + tmpDataTable.Rows[0]["SectionID"].ToString() + " ";
                        strSQL += "AND OrganizationID = " + modMain._CVariable._ORGANIZATIONID.ToString() + " ";
                       
                        tmpData = modMain._CDatabase.GetDataTable(strSQL);
                        if (tmpData.Rows.Count > 0)
                        {
                            txtRegAmount.Text =  (string) (tmpData.Rows[0]["Amount"]);
                        }
                        else
                        {
                            txtRegAmount.Text = "0";
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                LibraryManagement.CError.ShowError(ex, true, false.ToString(), "");
            }
        }





Code in VB.net in which no error
 Private Sub cmdSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSearch.Click
        Try
            Dim dlgStudentSearch As New frmStudentSearch
            Dim iStudentID As Int32
            Dim strCboSelection As String
            Dim tmpDataTable As DataTable
            Dim strSQL As String
            Dim tmpYear As DataTable
            Dim tmpData As DataTable
            Dim tmpCboDataTable As DataTable

            dlgStudentSearch.ShowForm()
            'MsgBox("Student Fees" + vbCrLf + "iStudentID :: " + _CConstant._iStudentID.ToString)
            iStudentID = _CConstant._iStudentID
            If iStudentID > 0 Then
                strCboSelection = "SELECT ID, Name FROM tblStudent"
                tmpCboDataTable = _CDatabase.GetDataTable(strCboSelection)
                CboStudentName.SelectedValue = iStudentID.ToString

                If Len(Trim(CboStudentName.Text)) <> 0 Then
                    strSQL = "SELECT BatchID FROM tblStudent "
                    strSQL += "WHERE ID = " + CboStudentName.SelectedValue.ToString + " "
                    tmpYear = _CDatabase.GetDataTable(strSQL)
                    If tmpYear.Rows.Count > 0 Then
                        If IsDBNull(tmpYear.Rows(0).Item("BatchID")) = True Then
                            MsgBox("Batch Not Present For This Student", MsgBoxStyle.Information)
                            cmdSave.Enabled = False
                            Exit Sub
                        Else
                            cmdSave.Enabled = True
                        End If
                    End If
                End If

                strSQL = "SELECT ClassID,SectionID FROM tblStudentDetail "
                strSQL += "WHERE StudentID = " + CboStudentName.SelectedValue.ToString + " "
                strSQL += "AND OrganizationID = " + _CVariable._ORGANIZATIONID.ToString + " "
                tmpDataTable = _CDatabase.GetDataTable(strSQL)
                If tmpDataTable.Rows.Count = 0 Then
                    MsgBox("No Student Details Present For This Student", MsgBoxStyle.Information)
                    cmdSave.Enabled = False
                    Exit Sub
                Else
                    cmdSave.Enabled = True
                End If

                If cmdSave.Enabled = True Then
                    strSQL = "SELECT Amount FROM tblLibraryStaticFees "
                    strSQL += "WHERE BatchID = " + tmpYear.Rows(0).Item("BatchID").ToString + " "
                    strSQL += "AND ClassID = " + tmpDataTable.Rows(0).Item("ClassID").ToString + " "
                    strSQL += "AND SectionID = " + tmpDataTable.Rows(0).Item("SectionID").ToString + " "
                    strSQL += "AND OrganizationID = " + _CVariable._ORGANIZATIONID.ToString + " "

                    tmpData = _CDatabase.GetDataTable(strSQL)
                    If tmpData.Rows.Count > 0 Then
                        txtRegAmount.Text = tmpData.Rows(0).Item("Amount")
                    Else
                        txtRegAmount.Text = 0
                    End If
                End If
            End If
        Catch ex As Exception
            CError.ShowError(ex, True, False)
        End Try
    End Sub


So what is doing wrong in c# code?