Problem on Checking the value already exist in the ComboBox in VB.NET

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  Which combobox control you are using? Also, is that the data from SQL are properly trimmed (remove whitespace)? I wrote a simple program and it works for me, below is the excerpt:

   

  Code Snippet

              //
              // comboBox1
              // 
              this.comboBox1.Items.AddRange(new object[] {
              "abc",
              "def",
              "ijk",
              "xyz"});

   

  Code Snippet

          private void button1_Click(object sender, EventArgs e)
          {
              if (comboBox1.Items.Contains(textBox1.Text))
                  MessageBox.Show("Yes!");
          }

  2008年5月12日 上午 01:42
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  Hi Jack
  
  Thanks for your information.
  
  I tried to use LTRIM and RTRIM on my SQL Query
  E.G.
  
  SQL Code
  ---------
  SELECT LTRIM(RTRIM(ValueCol)) AS ValueCol
  FROM MyTABLE
  
  
  VB Code
  ------
  ddl_AnalysisCode.DataSource=tbl '(the table is retrieve from Stored procedure from the SQL Above)
  
  ddl_ValueCol.DisplayMember="ValueCol"
  ddl_ValueCol.ValueMember="ValueCol"
  
  
  on the Button Click Event I have the code below
  
    MsgBox(ddl_ValueCol.SelectedValue)
    Dim a As String = ddl_ValueCol.SelectedValue
    MsgBox(ddl_ValueCol.Items.Contains(a))
  
  The first pop up display the selected value
  and the second pop up box always display false =(
  
  I am not sure what it like that.
  
  Could you give me some more suggestion please?

  2008年5月12日 上午 08:24
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  Hello ChiYau, 

   

  Contains() method checks the exact object which contained in this ComboBox. Because your ComboBox binds with the data in DataTable, the underling object in each item is DataRowView type. String typed value isn’t equal with DataRowView typed object. Thereby, contains method always retrun false.

   

  Please try the following method.

         

  Code Snippet

  private void button1_Click(object sender, EventArgs e)

          {

              string a=this.comboBox1.SelectedValue.ToString();  

              bool c = checkValue(a, this.comboBox1);

              MessageBox.Show(c.ToString());

             

          }

   

          public bool checkValue(string Value,ComboBox cb)

          {

              foreach (System.Data.DataRowView drv in cb.Items)

              {

                  if (Value.Equals(drv[cb.ValueMember]))

                      return true;

              }

              return false;

          }

   

   

  Hope this helps

  Wen Yuan

  2008年5月14日 下午 03:52
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  Hi Wen Yuan
  
  Thanks very much for your explaination, I understood now.
  
  Thanks a lot,
  
  

  2008年5月15日 上午 08:27