String Concat with inbetween operator

Question

User-1826049516 posted

Hi,

I'm having a complete mind blank for this.

I have 2 strings, one is formed from user entry in a Textbox control, the other is pulled from the database. Only if both are not blank, I need to insert "and" between them. The combined string is the basis of a DataView RowFilter.

private string SearchValue
{
	get
	{
		string _entry = Search_Text.Text; 'user input from textbox, can be empty
		string _default = UserDefaultSearch; 'property that pulls string from db based on current user, can be empty
		return String.Concat(_user, " and ", _default);
	}
}
...
...
...
DataView view;
view = <datasource>;
view.RowFilter = SearchValue;

As is, this will not work because if user input is empty the concat will have an invalid leading " and " and if _default is empty the concat will have an invalid trailing " and "

Thanks!

Answer 1

User-821857111 posted

You've probably solved it by now but:

return string.Concat(_user, string.IsNullOrEmpty(_user) || string.IsNullOrEmpty(_default) ? "" : " and ", _default);

Answer 2

User839733648 posted

Hi ldoodle,

To form a RowFilter value, specify the name of a column followed by an operator and a value to filter on. The value must be in quotation marks.

So you should write the SearchValue like "LastName = 'Smith'".

For more information about RowFilter, you could refer to: https://docs.microsoft.com/en-us/dotnet/api/system.data.dataview.rowfilter?view=netframework-4.7.2 

Please pay attention to the Remarks.

Besides, I've made a sample on my side, for more you could refer to the following code.

.aspx

    <form id="form1" runat="server">
        <div>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
        </div>
    </form>

code behind.

protected void Button1_Click(object sender, EventArgs e)
        {
            string constr = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                SqlDataAdapter sda = new SqlDataAdapter("SELECT * FROM tb_info",con);
                DataTable dt = new DataTable();
                sda.Fill(dt);
                DataSet ds = new DataSet();
                sda.Fill(ds);
                string _default = dt.Rows[0][1].ToString();
                string _entry = TextBox1.Text.ToString();
                string connectstring= String.Concat(_entry, " and ", _default);
                Response.Write(connectstring);

                DataView view = new DataView();
                view.Table = ds.Tables["tb_info"];
                view.RowFilter = "a='"+ connectstring + "'";
            }
        }

result:

Best Regards,

Jenifer