connection string manage with DropDownList - asp.net

Question

Suppose we have 5 companies with five database. Now the situation is we need to change the database path[connection string] on company name which is appear in dropdownlist. When we select the company name on selection of dropdown value we need to go to that companies database. How to do this in asp.net and what necessary changes do in web.config and dropdown event of company name.
now i tried:
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
if (DropDownList1.SelectedItem.Text.Equals("RVL LOGISTICS (I) PVT LTD"))
{
string cs = ConfigurationManager.ConnectionStrings["CompMasterConnectionString"].ConnectionString;
}
else if (DropDownList1.SelectedItem.Text.Equals("SIMONS SHIPPING PVT LTD"))
{
string vs = ConfigurationManager.ConnectionStrings["DUM01ConnectionString"].ConnectionString;
}
else
{
DropDownList2.Enabled = false;
}
}

Answer 1

PLease find below code to change the connection string dynamiccaly at runtime based on dropdown list selected text or value as per your need.
<asp:DropDownList ID="ddltest" AutoPostBack="True" OnSelectedIndexChanged="ddltest_OnSelectedIndexChanged" runat="server">
<asp:ListItem Text="CompanyName" Value="1"></asp:ListItem>
<asp:ListItem Text="CompanyName1" Value="2"></asp:ListItem>
</asp:DropDownList>
protected void ddltest_OnSelectedIndexChanged(object sender, EventArgs e)
{
var conString = "";
var ConStringName = "test";
switch (ddltest.SelectedItem.Text.ToLower())
{
case "CompanyName":
conString = GetConStringFromAppSetting("CompanyName");
AddUpdateConnectionString(conString, ConStringName);
break;
case "CompanyName1":
conString = GetConStringFromAppSetting("CompanyName1");
AddUpdateConnectionString(conString, ConStringName);
break;
}
}
private string GetConStringFromAppSetting(string test)
{
var constring = ConfigurationManager.AppSettings[test].Trim();
return constring;
}
private void AddUpdateConnectionString(string conStringValue, string conStringName)
{
var path = Server.MapPath("~/Web.Config");
var doc = new XmlDocument();
doc.Load(path);
if (doc.DocumentElement != null)
{
var list = doc.DocumentElement.SelectNodes(string.Format("connectionStrings/add[#name='{0}']", conStringName));
if (list != null)
{
var node = list[0];
if (node.Attributes != null) node.Attributes["connectionString"].Value = conStringValue;
}
}
doc.Save(path);
}
in Above code i changed your if else block to switch block, which helps to read code nicely. It will check the selected text value from the dropdown.
First Method is GetConStringFromAppSetting. It will accept the selected Text of dropdown and it will check the same in AppSetting Section of WebConfig and get the value from that.
In the AppSetting of Web Config do work like below:
<appSettings>
<add key="CompanyName" value="constringOfThatCompany" />
<add key="CompanyName1" value="constringOfThatCompany1" />
</appSettings>
After that there is method is AddUpdateConnectionString. IT will accept the Constring value which is recevied from from above method and default connection string name.
After that in that method:
Load the config file.
Load that file in XMLDOcument so we can parse easily.
3.Find the connection string node by name we have parsed.
Set the value of that node that connection string value.
Save the document (web.COnfig) Again.
Note: It is not the good way to change the web config like this. one can provide other secure way.