string-length in XSLT not working

Question

I have written the following code which checks whether the string provided is greater than 1- characters in which case only print the first 10 characters, otherwise print complete string. But I am getting error "Unable to display this web part" probably due to some bug in my syntax. Please check.

<xsl:template name="ShortenDetail">
    <xsl:param name="String">
        <xsl:choose>
            <xsl:when test="string-length($String) &gt; '10'">
                <xsl:value-of select="substring($String, 0,9)"></xsl:value-of>
            </xsl:when>
            <xsl:otherwise>
                <xsl:value-of select="$String"></xsl:value-of>
            </xsl:otherwise>
        </xsl:choose>
    </xsl:param>
</xsl:template>

EDIT
And please also tell me how to use this function within a function in xslt. Following is the code which I am already using in my XSLT. This function cleans the "Detail" column that I am receiving from list and then after that I want to apply ShortenDetail function (mentioned above) but I don't know how to do that.

<xsl:call-template name="RemoveHtml">
       <xsl:with-param name="String" select="@Detail"/>
</xsl:call-template>

I tried using like this but getting error:

<xsl:call-template name="ShortenDetail">
     <xsl:call-template name="RemoveHtml">
           <xsl:with-param name="String" select="@Detail"/>
     </xsl:call-template>
</xsl:call-template>

Answer 1

The way you have this written at the moment you seem to be trying to set the value of the parameter. I think the parameter tag should be closed before you start the choose.

EDIT: to reflect the changes to the question - I think this is what you are trying to achieve?

<xsl:template name="ShortenDetail">
    <xsl:variable name="String">
        <xsl:call-template name="RemoveHtml">
            <xsl:with-param name="String" select="@Detail"/>
        </xsl:call-template>
    </xsl:variable>
    <xsl:choose>
        <xsl:when test="string-length($String) &gt; '10'">
            <xsl:value-of select="substring($String, 0,9)"></xsl:value-of>
        </xsl:when>
        <xsl:otherwise>
            <xsl:value-of select="$String"></xsl:value-of>
        </xsl:otherwise>
    </xsl:choose>
</xsl:template>