Error does not indicate an object instance
I use it DevExpress
I'm trying to add a new group, and add it to ComboBoxEdit, but the error shows that it does not indicate an object instance.
I pass the parameter in different forms... How can I do?
1 form InformationOfStudents:
public void LoadingIDGroupTeacher(string indexTeacher)
{
sqlConnection = new SqlConnection(connectionString);
string sql = "GETGroupsTeacher";
sqlConnection.Open();
sqlCommand = new SqlCommand(sql, sqlConnection)
{
CommandType = System.Data.CommandType.StoredProcedure
};
sqlParameter = new SqlParameter
{
ParameterName = "@index",
Value = int.Parse(indexTeacher)
};
sqlCommand.Parameters.Add(sqlParameter);
sqlDataReader = sqlCommand.ExecuteReader();
while (sqlDataReader.Read())
{
//an error appears here
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
}
sqlConnection.Close();
}
2 form when I want to add a new group:
private void BtnCancel_Click(object sender, EventArgs e)
{
new InformaitionOfStudents().LoadingIDGroupTeacher(usIndex);
Dispose();
}
T-SQL procedures:
ALTER PROCEDURE [dbo].[GETGroupsTeacher]
@index int
AS
SELECT NameGroup FROM dbo.Groups WHERE Teacher = @index
c# winforms
asked Dec 27 '18 at 20:05
Юрий Куликовский
212
add a comment |
I use it DevExpress
I'm trying to add a new group, and add it to ComboBoxEdit, but the error shows that it does not indicate an object instance.
I pass the parameter in different forms... How can I do?
1 form InformationOfStudents:
public void LoadingIDGroupTeacher(string indexTeacher)
{
sqlConnection = new SqlConnection(connectionString);
string sql = "GETGroupsTeacher";
sqlConnection.Open();
sqlCommand = new SqlCommand(sql, sqlConnection)
{
CommandType = System.Data.CommandType.StoredProcedure
};
sqlParameter = new SqlParameter
{
ParameterName = "@index",
Value = int.Parse(indexTeacher)
};
sqlCommand.Parameters.Add(sqlParameter);
sqlDataReader = sqlCommand.ExecuteReader();
while (sqlDataReader.Read())
{
//an error appears here
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
}
sqlConnection.Close();
}
2 form when I want to add a new group:
private void BtnCancel_Click(object sender, EventArgs e)
{
new InformaitionOfStudents().LoadingIDGroupTeacher(usIndex);
Dispose();
}
T-SQL procedures:
ALTER PROCEDURE [dbo].[GETGroupsTeacher]
@index int
AS
SELECT NameGroup FROM dbo.Groups WHERE Teacher = @index
c# winforms
asked Dec 27 '18 at 20:05
Юрий Куликовский
212
2
Please edit and give the complete actual error message
– WelcomeOverflow
Dec 27 '18 at 20:07
3
CallingDispose()on what I'm assuming is a form in a WinForms button click handler is likely not going to end well. You are Disposing of something that is in the midst of having called your handler.
– Flydog57
Dec 27 '18 at 20:18
add a comment |
I use it DevExpress
I'm trying to add a new group, and add it to ComboBoxEdit, but the error shows that it does not indicate an object instance.
I pass the parameter in different forms... How can I do?
1 form InformationOfStudents:
public void LoadingIDGroupTeacher(string indexTeacher)
{
sqlConnection = new SqlConnection(connectionString);
string sql = "GETGroupsTeacher";
sqlConnection.Open();
sqlCommand = new SqlCommand(sql, sqlConnection)
{
CommandType = System.Data.CommandType.StoredProcedure
};
sqlParameter = new SqlParameter
{
ParameterName = "@index",
Value = int.Parse(indexTeacher)
};
sqlCommand.Parameters.Add(sqlParameter);
sqlDataReader = sqlCommand.ExecuteReader();
while (sqlDataReader.Read())
{
//an error appears here
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
}
sqlConnection.Close();
}
2 form when I want to add a new group:
private void BtnCancel_Click(object sender, EventArgs e)
{
new InformaitionOfStudents().LoadingIDGroupTeacher(usIndex);
Dispose();
}
T-SQL procedures:
ALTER PROCEDURE [dbo].[GETGroupsTeacher]
@index int
AS
SELECT NameGroup FROM dbo.Groups WHERE Teacher = @index
c# winforms
asked Dec 27 '18 at 20:05
Юрий Куликовский
212
I use it DevExpress
I'm trying to add a new group, and add it to ComboBoxEdit, but the error shows that it does not indicate an object instance.
I pass the parameter in different forms... How can I do?
1 form InformationOfStudents:
public void LoadingIDGroupTeacher(string indexTeacher)
{
sqlConnection = new SqlConnection(connectionString);
string sql = "GETGroupsTeacher";
sqlConnection.Open();
sqlCommand = new SqlCommand(sql, sqlConnection)
{
CommandType = System.Data.CommandType.StoredProcedure
};
sqlParameter = new SqlParameter
{
ParameterName = "@index",
Value = int.Parse(indexTeacher)
};
sqlCommand.Parameters.Add(sqlParameter);
sqlDataReader = sqlCommand.ExecuteReader();
while (sqlDataReader.Read())
{
//an error appears here
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
}
sqlConnection.Close();
}
2 form when I want to add a new group:
private void BtnCancel_Click(object sender, EventArgs e)
{
new InformaitionOfStudents().LoadingIDGroupTeacher(usIndex);
Dispose();
}
T-SQL procedures:
ALTER PROCEDURE [dbo].[GETGroupsTeacher]
@index int
AS
SELECT NameGroup FROM dbo.Groups WHERE Teacher = @index
c# winforms
c# winforms
asked Dec 27 '18 at 20:05
Юрий Куликовский
212
asked Dec 27 '18 at 20:05
Юрий Куликовский
212
asked Dec 27 '18 at 20:05
Юрий Куликовский
212
asked Dec 27 '18 at 20:05
Юрий Куликовский
212
asked Dec 27 '18 at 20:05
Юрий Куликовский
212
212
2
Please edit and give the complete actual error message
– WelcomeOverflow
Dec 27 '18 at 20:07
3
CallingDispose()on what I'm assuming is a form in a WinForms button click handler is likely not going to end well. You are Disposing of something that is in the midst of having called your handler.
– Flydog57
Dec 27 '18 at 20:18
add a comment |
2
Please edit and give the complete actual error message
– WelcomeOverflow
Dec 27 '18 at 20:07
3
CallingDispose()on what I'm assuming is a form in a WinForms button click handler is likely not going to end well. You are Disposing of something that is in the midst of having called your handler.
– Flydog57
Dec 27 '18 at 20:18
2
2
Please edit and give the complete actual error message
– WelcomeOverflow
Dec 27 '18 at 20:07
Please edit and give the complete actual error message
– WelcomeOverflow
Dec 27 '18 at 20:07
3
3
Calling
Dispose() on what I'm assuming is a form in a WinForms button click handler is likely not going to end well. You are Disposing of something that is in the midst of having called your handler.– Flydog57
Dec 27 '18 at 20:18
Calling
Dispose() on what I'm assuming is a form in a WinForms button click handler is likely not going to end well. You are Disposing of something that is in the midst of having called your handler.– Flydog57
Dec 27 '18 at 20:18
add a comment |
2 Answers
2
active
oldest
votes
Add:
if(!sqlDataReader.IsDBNull(0))
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
Or:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0)?.ToString() ?? "");
answered Dec 27 '18 at 21:06
Shimon Lebovits
634
add a comment |
If ComboBoxGroups is a DevExpress DevExpress.Xpf.Editors.ComboBoxEdit control you should probably use:
ComboBoxGroups.Items.Add(sqlDataReader.GetValue(0).ToString());
and not:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
And the Dispose(); in the button event handler in "2 form" will Dispose the dialog "2 form" so that's probably not a good idea.
answered Dec 27 '18 at 22:09
Jens Granlund
4,14312427
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Add:
if(!sqlDataReader.IsDBNull(0))
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
Or:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0)?.ToString() ?? "");
answered Dec 27 '18 at 21:06
Shimon Lebovits
634
add a comment |
Add:
if(!sqlDataReader.IsDBNull(0))
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
Or:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0)?.ToString() ?? "");
answered Dec 27 '18 at 21:06
Shimon Lebovits
634
add a comment |
Add:
if(!sqlDataReader.IsDBNull(0))
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
Or:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0)?.ToString() ?? "");
answered Dec 27 '18 at 21:06
Shimon Lebovits
634
Add:
if(!sqlDataReader.IsDBNull(0))
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
Or:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0)?.ToString() ?? "");
answered Dec 27 '18 at 21:06
Shimon Lebovits
634
edited Dec 27 '18 at 21:49
answered Dec 27 '18 at 21:06
Shimon Lebovits
634
answered Dec 27 '18 at 21:06
Shimon Lebovits
634
answered Dec 27 '18 at 21:06
Shimon Lebovits
634
634
add a comment |
add a comment |
If ComboBoxGroups is a DevExpress DevExpress.Xpf.Editors.ComboBoxEdit control you should probably use:
ComboBoxGroups.Items.Add(sqlDataReader.GetValue(0).ToString());
and not:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
And the Dispose(); in the button event handler in "2 form" will Dispose the dialog "2 form" so that's probably not a good idea.
answered Dec 27 '18 at 22:09
Jens Granlund
4,14312427
add a comment |
If ComboBoxGroups is a DevExpress DevExpress.Xpf.Editors.ComboBoxEdit control you should probably use:
ComboBoxGroups.Items.Add(sqlDataReader.GetValue(0).ToString());
and not:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
And the Dispose(); in the button event handler in "2 form" will Dispose the dialog "2 form" so that's probably not a good idea.
answered Dec 27 '18 at 22:09
Jens Granlund
4,14312427
add a comment |
If ComboBoxGroups is a DevExpress DevExpress.Xpf.Editors.ComboBoxEdit control you should probably use:
ComboBoxGroups.Items.Add(sqlDataReader.GetValue(0).ToString());
and not:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
And the Dispose(); in the button event handler in "2 form" will Dispose the dialog "2 form" so that's probably not a good idea.
answered Dec 27 '18 at 22:09
Jens Granlund
4,14312427
If ComboBoxGroups is a DevExpress DevExpress.Xpf.Editors.ComboBoxEdit control you should probably use:
ComboBoxGroups.Items.Add(sqlDataReader.GetValue(0).ToString());
and not:
ComboBoxGroups.Properties.Items.Add(sqlDataReader.GetValue(0).ToString());
And the Dispose(); in the button event handler in "2 form" will Dispose the dialog "2 form" so that's probably not a good idea.
answered Dec 27 '18 at 22:09
Jens Granlund
4,14312427
answered Dec 27 '18 at 22:09
Jens Granlund
4,14312427
answered Dec 27 '18 at 22:09
Jens Granlund
4,14312427
answered Dec 27 '18 at 22:09
Jens Granlund
4,14312427
4,14312427
add a comment |
add a comment |
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2
Please edit and give the complete actual error message
– WelcomeOverflow
Dec 27 '18 at 20:07
3
Calling
Dispose()on what I'm assuming is a form in a WinForms button click handler is likely not going to end well. You are Disposing of something that is in the midst of having called your handler.– Flydog57
Dec 27 '18 at 20:18