我如何制作组合框中的第一项是---选择---在c＃winapp中 [英] How i make the first item in combobox is ---select--- in c# winapp

问题描述

  public   void  FillComboCity（）
 {
 DataSet dSet =  new  DataSet（）; 
 尝试 
 {
 con.Open（）; 
 s =  选择City_id，City_Name from City; 
 sCommand =  new  SqlCommand（s，con）; 
 sdAdapter =  new  SqlDataAdapter（）; 
 sdAdapter.SelectCommand = sCommand; 
 sdAdapter.Fill（dSet）; 
 CB_City.ValueMember =   City_id; 
 CB_City.DisplayMember =   City_Name; 
 CB_City.DataSource = dSet.Tables [ 0 ]; 
 CB_City.Items.Insert（-1，  ---选择--- ）; 
 con.Close（）; 
} 
  catch  
 {
  return ; 
} 
} 
 
 私有  void  FRM_PatientData_Load（  object  sender，EventArgs e）
 {
 FillComboCity（）; 
} 

我的尝试：



i想要添加---选择 - 在组合框中的第一项中

解决方案

尝试使用以下代码：

< pre lang =c＃> DataSet dSet = new DataSet（）;
尝试
{
con.Open（）;
s = 选择City_id，City_Name from City;
sCommand = new SqlCommand（s，con）;
sdAdapter = new SqlDataAdapter（）;
sdAdapter.SelectCommand = sCommand;
sdAdapter.Fill（dSet）;
CB_City.ValueMember = City_id;
CB_City.DisplayMember = City_Name;
CB_City.DataSource = dSet.Tables [ 0 ];
CB_City.Items.Insert（ 0 ， ---选择---）;
DataRow dr = dSet.Tables [ 0 ]。NewRow（）;
dr [ City_Name] = - 选择 - ;
dr [ City_id] = 0 ;

dSet.Tables [ 0 ]。Rows.InsertAt（dr， 0 ）;
CB_City.SelectedIndex = 0 ;

con.Close（）;
}

试试这个。注意我在DisplayMember指示的DataColumn中向数据表添加了一个新行：--- select--：

  public   void  FillComboCity（）
 {
 DataSet dSet =  new  DataSet（）; 
 尝试 
 {
 con.Open（）; 
 s =  选择City_id，City_Name from City; 
 sCommand =  new  SqlCommand（s，con）; 
 sdAdapter =  new  SqlDataAdapter（）; 
 sdAdapter.SelectCommand = sCommand; 
 sdAdapter.Fill（dSet）; 
 DataRow dr = dSet.Tables [ 0 ]。NewRow（）; 
 dr.ItemArray =  new   object  [ 2 ] { 0 ，  ---选择 - }; 
 dSet.Tables [ 0 ]。Rows.InsertAt（dr， 0 ）; 
 CB_City.ValueMember =   City_id; 
 CB_City.DisplayMember =   City_Name; 
 CB_City.DataSource = dSet.Tables [ 0 ]; 
 con.Close（）; 
} 
  catch  
 {
  return ; 
} 
} 

public void FillComboCity()
        {          
            DataSet dSet = new DataSet();
            try
            {
                con.Open();
                s = "select City_id , City_Name from City";
                sCommand = new SqlCommand(s, con);
                sdAdapter = new SqlDataAdapter();
                sdAdapter.SelectCommand = sCommand;
                sdAdapter.Fill(dSet);
                CB_City.ValueMember = "City_id";
                CB_City.DisplayMember = "City_Name";
                CB_City.DataSource = dSet.Tables[0];
                CB_City.Items.Insert(-1, "---Select---");
                con.Close();
            }
            catch
            {
                return;
            }
        }

        private void FRM_PatientData_Load(object sender, EventArgs e)
        {
            FillComboCity();
        }

What I have tried:

i want add ---select-- in firt item in combobox

解决方案

Try with below code:

DataSet dSet = new DataSet();
try
{
	con.Open();
	s = "select City_id , City_Name from City";
	sCommand = new SqlCommand(s, con);
	sdAdapter = new SqlDataAdapter();
	sdAdapter.SelectCommand = sCommand;
	sdAdapter.Fill(dSet);
	CB_City.ValueMember = "City_id";
	CB_City.DisplayMember = "City_Name";
	CB_City.DataSource = dSet.Tables[0];
	CB_City.Items.Insert(0, "---Select---");
	DataRow dr = dSet.Tables[0].NewRow();
	dr["City_Name"] = "--Select--";
	dr["City_id"] = 0;

	dSet.Tables[0].Rows.InsertAt(dr, 0);
	CB_City.SelectedIndex = 0;
	
	con.Close();
}

Try this. Notice I'm adding a new row to the datatable with the "---select--" in the DataColumn indicated by DisplayMember:

public void FillComboCity()
{          
    DataSet dSet = new DataSet();
    try
    {
          con.Open();
          s = "select City_id , City_Name from City";
          sCommand = new SqlCommand(s, con);
          sdAdapter = new SqlDataAdapter();
          sdAdapter.SelectCommand = sCommand;
          sdAdapter.Fill(dSet);
          DataRow dr= dSet.Tables[0].NewRow();
          dr.ItemArray=new object[2]{0,"---Select--"};
          dSet.Tables[0].Rows.InsertAt(dr, 0);
          CB_City.ValueMember = "City_id";
          CB_City.DisplayMember = "City_Name";
          CB_City.DataSource = dSet.Tables[0];
          con.Close();
     }
     catch
     {
          return;
     }
}

这篇关于我如何制作组合框中的第一项是---选择---在c＃winapp中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！