Filtering the XML Node binded with dropdownlist

[sachtech boy]

Hello Friends, I have two DropDownList: 1) CollegeDDL which contains Four static names of the colleges. : Homeopathic Medical College,Physiotherapy College,Institute of Ayurveda,Institute of Business Administration


2) CourseDDL which is bind to CourseDetail.XML.

<Institutes>
<Institute>
<InstituteName> Homoeopathic Medical College </InstituteName>
<Course> <CourseName> BHMS </CourseName> </Course>
<Course> <CourseName> MD(Repertary) </CourseName> </Course>
<Course> <CourseName> MD(Organon of Medicine) </CourseName> </Course>
<Course> <CourseName> MD(Materia Medica) </CourseName> </Course>
</Institute>

<Institute>
<InstituteName> Physiotherapy College </InstituteName>
<Course> <CourseName> BPT </CourseName> </Course>
<Course> <CourseName> BPT(Sports) </CourseName> </Course>
<Course> <CourseName> BPT(Cardio) </CourseName> </Course>
</Institute>

<Institute>
<InstituteName> Institute of Ayurved </InstituteName>
<Course> <CourseName> BAMS </CourseName> </Course>
<Course> <CourseName> BAMS(Nature) </CourseName> </Course>
<Course> <CourseName> BAMS(Plants) </CourseName> </Course>
</Institute>

<Institute>
<InstituteName> Institute of Business Administration </InstituteName>
<Course> <CourseName>BBA</CourseName> </Course>
<Course> <CourseName>DBM</CourseName> </Course>
<Course> <CourseName>BBA(Distance)</CourseName> </Course>
</Institute>

---------------------------------
CourseDetail.XSL

<xsl:template match ="/">

<Institute>
<xsl:apply-templates select ="Institutes/Institute/Course"/>
</Institute>

</xsl:template>


<xsl:template match ="Institutes/Institute/Course">
<Institute>
<xsl:attribute name="CourseName">
<xsl:value-of select="CourseName"/>
</xsl:attribute>
</Institute>

</xsl:template>

</xsl:stylesheet>
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I have bind Coursedetail.XML to CourseDDL and CourseDetail.XSL (No XPATH Expression)

After doing this, My CourseDDL is correctly filled with all the CourseName value of my XML file.
But now I want to filter the data bound to CourseDDL , based on College Name selected in CollegeDDL.

For Example:Currently my CourseDDL contains all the CourseName : BHMS,MD(Repertary),MD(Organon of Medicine),......,DBM,BBA(Distance).

But when I select "Homoeopathic Medical College" in CollegeDDL , The data bound to CourseDDL should filter accordingly.
It means when I select "Homoeopathic Medical College" , my CourseDDL should Display only that course: BHMS,MD(Repertary),MD(Organon of Medicine),MD(Materia Medica)

------------------------------------
I have tried the following , but could not achieve it.

1) XmlDataSourceCourse.XPath = "/Institutes/Institute[InstituteName='" + CollegeDDL.SelectedItem.Value + "']"

2) XmlDataSourceCourse.XPath = "/Institutes/Institute[InstituteName='" + ddlinstitute.SelectedItem.Value + "']/Course"

3)XmlDataSourceCourse.XPath = "/Institutes/Institute[InstituteName='" + ddlinstitute.SelectedItem.Value + "']/Course/CourseName"


Anybody please help to format correct XPATH Expression to achive this.